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Often misunderstood, always awesome, the turbo is one of the greatest gifts to the automotive world.

At its core, an engine is an air pump, which creates the byproduct of horsepower and torque. A turbo simply increases the engine’s ability and efficiency in regards to moving air in and out of the engine. Rather than relying on the engine’s vacuum to suck air into the engine, a turbo forces the air into the engine.

A turbo has a few basic parts. Two wheels, which resemble fans, are attached to each other with a rod. The fans sit inside housings. The center section resides between the two housings and holds the bearings, as well as the oil journals and the cooling jackets.

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Whatever your relationship with the automobile, it is important to understand who built it. The trouble with auto manufacturers is that they are always building stuff for each other. This post will help sort out who built what, for who, and why it matters.

First thing first, let’s get acquainted with the major automotive families. Automotive families are different makes that are all made by the same manufacture. Many times manufactures will want to produce a regular run of vehicles, and then a more luxurious run of models. They will produce what is essentially the same vehicle, but badge them differently and pack one with all the high end wonders people love.

The major automotive families include …

Toyota, Lexus, and Scion. Honda and Acura. Nissan and Infinity. Hyundai and Kia. BMW and Mini. Volkswagen, Audi, Skoda and Seat. Jaguar and Land Rover. Ford, Lincoln, and Mercury. Dodge, Chrysler, Jeep, Plymouth and Eagle (Here shortly, toss in Fiat). General Motors, Chevrolet, Oldsmobile, Cadillac, Pontiac, Buick, Hummer, Saturn, and GMC (As well as Opel, Vauxhall, Holden and Daewoo). You can always tell a terrible product, because they will have numerous names for the same bad product.
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When it comes to automotive repair, there are several methods of approaching the problem. Let’s look at: known problems first, maintenance as pair, comprehensive versus fix just what is broken, as well as a few diagnostic approaches.

Known Problems First

Until we correct all the known problems in a system, we can not know if they are effecting the portion of the system we are concerned about. Often times tracking down the cause of one problem will reveal the cause of others. Use this method with a bit of common sense, replacing a gas cap for an evaporative leak will most likely not fix a misfire. However, often times vacuum leaks cause many, many problems. (For a specific example of fix know problems first, visit here )
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Here is a list of the most common check engine lights (CELs P Codes) and their common causes and common symptoms.

To diagnose many of the problems, you will need little more than a test light, a volt meter, a vacuum gauge and maybe a can of brake clean. A hand held code puller/ data reader such as this….

This is a relatively inexpensive scan tool made by autolink. It pulls codes as well as reads and displays your basic drive-ability data. I would recommend this to anyone who wants to repair any modern car (1996 or newer). I have one, and I use it all day long. It is very handy.

automotive repair scan tool

Oxygen sensor codes

Oxygen sensor codes generally mean the oxygen sensor has failed. The oxygen sensor is in the exhaust, and reads the exhaust in order for the computer to finely tune the amount of fuel the engine needs.

Oxygen Sensor

Bank 1 sensor is on the side of the motor with the number one cylinder, bank 2 is the other side. Sensor 1 is in the exhaust, on the motor side (upstream) of the catalytic converter, sensor 2 is on the other side (down stream) of the cat. Check and make sure the sensor has power, ground and it’s reference voltage (usually 5 or 1 volts). The signal should switch back and forth between low and high voltage.

Make sure the vehicle is not stuck in a lean or rich condition. Introduce a vacuum leak, and see if the signal voltage changes. Then add fuel (brake clean through a vacuum port) and see if the signal changes. 6 times out of 10 the sensor is bad, 3 times out of 10 there is a vacuum leak or rich condition. The codes that are for heater circuit are almost always the sensor, otherwise there is a broken wire somewhere.

Symptoms include, poor gas mileage, poor power, rough idle, fail emission testing. Vehicle should start and run even if the oxygen sensor is unplugged.

  • P0051 HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
  • P0052 HO2S Heater Control Circuit High (Bank 2 Sensor 1)
  • P0130 02 Sensor Circuit Malfunction (Bank 1 Sensor 1)
  • P0131 02 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
  • P0132 02 Sensor Circuit High Voltage (Bank 1 Sensor 1)
  • P0133 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
  • P0134 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
  • P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
  • P0136 02 Sensor Circuit Malfunction (Bank 1 Sensor 2)
  • P0137 02 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
  • P0138 02 Sensor Circuit High Voltage (Bank 1 Sensor 2)
  • P0139 02 Sensor Circuit Slow Response (Bank 1 Sensor 2)
  • P0140 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)
  • P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
  • P0150 02 Sensor Circuit Malfunction (Bank 2 Sensor 1)
  • P0151 02 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
  • P0152 02 Sensor Circuit High Voltage (Bank 2 Sensor 1)
  • P0153 02 Sensor Circuit Slow Response (Bank 2 Sensor 1)
  • P0154 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
  • P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
  • P0156 02 Sensor Circuit Malfunction (Bank 2 Sensor 2)
  • P0157 02 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
  • P0158 02 Sensor Circuit High Voltage (Bank 2 Sensor 2)
  • P0159 02 Sensor Circuit Slow Response (Bank 2 Sensor 2)
  • P0160 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)
  • P0161 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

Mass Air Flow (MAF) Codes

Mass Air Flow (MAF) Codes generally mean the MAF has gone bad or there is a major vacuum leak. The MAF is the main way the engine monitors the amount of air going into the engine in order to determine how much fuel the engine needs.

Mass Air Flow Sensor

First and foremost check to see if there are any vacuum leaks. Watch your short term and long term fuel trims. If there is a vacuum leak, they should be adding fuel. Spray the intake and intake manifold with brake clean and look for the fuel trims to go back to 0, and even start pulling fuel. If the fuel trims, particularly the short term trims, pull fuel, you have found a vacuum leak.

Check and make sure the sensor has power, ground and it’s reference voltage (usually 5 or 1 volts). If the car runs with a MAF code, tap the MAF while the engine is running and see if the engine bobbles or dies. Often times a bad MAF will cause the engine to not start.

Other symptoms would be extremely poor gas mileage, extremely poor running condition, and fail emission testing. 5 times out of 10 the sensor is bad, 4 times out of 10 there is a vacuum leak.

  • P0100 Mass or Volume Air Flow Circuit Malfunction
  • P0101 Mass or Volume Air Flow Circuit Range/Performance Problem
  • P0102 Mass or Volume Air Flow Circuit Low Input
  • P0103 Mass or Volume Air Flow Circuit High Input
  • P0104 Mass or Volume Air Flow Circuit Intermittent

Manifold Absolute Pressure (MAP)

Manifold Absolute Pressure (MAP) codes generally mean the MAP is bad, or there is a major vacuum leak. The MAP sensor is one major way the computer decides how much fuel the engine needs. Some cars have a stand alone MAP, some have a MAP sensor built into the MAF.

First and foremost check to see if there are any vacuum leaks. Cars that use only a MAP to meter fuel will often be rich if there is a vacuum leak. Watch your short term and long term fuel trims. Spray the intake and intake manifold with brake clean and look for the fuel trims to start pulling fuel. If the fuel trims, particularly the short term trims, pull fuel, you have found a vacuum leak.

Check and make sure the sensor has power, ground and it’s reference voltage (usually 5 or 1 volts). Also make sure there is good vacuum going into the MAP sensor.

Often times a bad MAP will cause the engine to not start. Other symptoms would be extremely poor gas mileage, extremely poor running condition, and fail emission testing. 5 times out of 10 the sensor is bad, 4 times out of 10 there is a vacuum leak.

  • P0105 Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction
  • P0106 Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
  • P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

Engine Coolant Temperature (ECT)

Engine Coolant Temperature (ECT) codes generally mean the coolant temperature sensor is bad, or the car is out of coolant. The ECT effects the amount of fuel the computer supplies the engine. Engines need more fuel to start and run when they are cold. Keep in mind the engine almost always has two ECT sensors, one for the gauge and one for the computer.

Wait for the car to cool down, and make sure it is full of coolant. If the car is full of coolant, put a new sensor in, they are cheep and easy.

Symptoms of a bad ECT sensor include, poor gas mileage, hard to start, no start, car over heating due to cooling fans not coming on, and fail emission testing. Very common failure on all makes, remember there are almost always two, two wire ECT sensors, one for the gauge one for the computer.

6 out of 10 times the sensor is bad, 4 out of 10 times the vehicle is low on coolant.

  • P0115 Engine Coolant Temperature Circuit Malfunction
  • P0116 Engine Coolant Temperature Circuit Range/Performance Problem
  • P0117 Engine Coolant Temperature Circuit Low Input
  • P0118 Engine Coolant Temperature Circuit High Input

Throttle Position Sensor (TPS)

Throttle Position Sensor (TPS) codes generally mean the TPS is bad, or the throttle plate is some how out of adjustment. The throttle body may be dirty, the throttle cable may be to tight, the throttle adjustment screw may need to be tweaked. If the vehicle is drive by wire ( a vehicle which does not have a throttle cable) the throttle body may just need to be reset through a factory type scan tool.

Symptoms include poor or no throttle response, poor gas mileage, low or high idle, improper shifting ( with automatic transmissions).

8 out of 10 times the sensor is bad.

  • P0121 Throttle Position Sensor/Switch A Circuit Range/Performance Problem
  • P0122 Throttle Position Sensor/Switch A Circuit Low Input
  • P0123 Throttle Position Sensor/Switch A Circuit High Input

Coolant temperature too low

The vehicle is not reaching operating temperatures. Almost always a thermostat stuck open, but can also be a faulty engine coolant temperature sensor.

Symptoms include poor gas mileage.

P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control
P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

Gross fuel trim failure

Gross fuel trim failure are common and have multiple causes. Vacuum leak, bad oxygen sensor, fuel leaking from fuel pressure regulator into manifold, failed fuel injector, bad coolant temperature (ECT) sensor, bad manifold pressure (MAP) sensor, bad mass air flow (MAF) sensor.

First determine if the trims are lean or rich. Then go down the list of causes until you find a gross failure. ECT sensor reading 0 degrees even though the vehicle is hot. A MAP or MAF sensor at 0 volts. A Major vacuum leak, the kind you can hear and is the size of your finger. Generally gross fuel trim failures are easy to find.

P0170 Fuel Trim Malfunction (Bank 1)
P0171 System too Lean (Bank 1)
P0172 System too Rich (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)
P0174 System too Lean (Bank 2)
P0175 System too Rich (Bank 2)

Misfire

Misfire codes – suck, squish, bang, blow gone wrong. Poor quality or incorrect ignition parts, failed injector, burnt valve, improper camshaft/ crankshaft timing, improper ignition timing, low quality gas (water in fuel), low compression (bad rings).

If you have a particular cylinder misfire, then it is a little easier to find the cause. If you have several misfires, or a random/ multiple misfires, check all the cylinders and also pay close attention to fuel trims. Pull the spark plug, check to ensure it is the proper plug. Check the gap and look for a burn mark down the side. Do a compression check. If compression is low, proceed with a leak down test.

If compression is good, put the plug back in and run the vehicle with a ignition stress tester in line.

Ignition Tester

This is a tester you can put in line in your ignition system. By making the spark jump a gap, you can stress the ignition system and find a failing system. Very handy. If the spark is ok, check to ensure you injector is clicking.

If you suspect a faulty part, (coil, spark plug, injector) you can always move that one part to another cylinder, clear the codes and then see if the misfire moves to the new cylinder.

P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0307 Cylinder 7 Misfire Detected
P0308 Cylinder 8 Misfire Detected
P0309 Cylinder 9 Misfire Detected
P0310 Cylinder 10 Misfire Detected
P0311 Cylinder 11 Misfire Detected
P0312 Cylinder 12 Misfire Detected

Knock sensor

Knock sensor codes generally mean the knock sensor has gone bad. Can be wiring, almost never is. Very common problem on imports.

P0325 Knock Sensor 1 Circuit Malfunction (Bank I or Single Sensor)
P0326 Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single sensor)
P0327 Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)
P0328 Knock Sensor 1 Circuit High Input (Bank I or Single Sensor)
P0329 Knock Sensor 1 Circuit Intermittent (Bank 1 or Single Sensor)
P0330 Knock Sensor 2 Circuit Malfunction (Bank 2)
P0331 Knock Sensor 2 Circuit Range/Performance (Bank 2)
P0332 Knock Sensor 2 Circuit Low Input (Bank 2)
P0333 Knock Sensor 2 Circuit High Input (Bank 2)
P0334 Knock Sensor 2 Circuit Intermittent (Bank 2)

Crankshaft Position

Crankshaft Position generally means the sensor has gone bad, or a timing belt that has skipped a tooth. Many vehicles, particularly Audi and VW will throw a Crankshaft Position if the are turned over too many times with out starting. For example, if the fuel pump goes out, and you try long enough to start the car, a Crankshaft Position code will appear.

P0335 Crankshaft Position Sensor A Circuit Malfunction
P0336 Crankshaft Position Sensor A Circuit Range/Performance
P0337 Crankshaft Position Sensor A Circuit Low Input
P0338 Crankshaft Position Sensor A Circuit High Input
P0339 Crankshaft Position Sensor A Circuit Intermittent

Camshaft Position

Camshaft Position generally means the sensor has gone bad or a timing belt that has skipped a tooth. Could also be a clogged or failed variable valve timing solenoid gone bad. Generally, a vehicle uses the crankshaft position sensor for gross fuel and spark control, and the camshaft position sensor for fine tuning. Therefore, a bad camshaft sensor may cause a rough idle, or poor gas mileage, or poor performance, but may the vehicle will still run. On other cars loss of a camshaft position sensor will cause the vehicle to not start at all.

P0340 Camshaft Position Sensor Circuit Malfunction
P0341 Camshaft Position Sensor Circuit Range/Performance
P0342 Camshaft Position Sensor Circuit Low Input
P0343 Camshaft Position Sensor Circuit High Input
P0344 Camshaft Position Sensor Circuit Intermittent
P0345 Camshaft Position Sensor A Circuit Malfunction (Bank 2)
P0346 Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
P0347 Camshaft Position Sensor A Circuit Low Input (Bank 2)
P0348 Camshaft Position Sensor A Circuit High Input (Bank 2)
P0349 Camshaft Position Sensor A Circuit Intermittent (Bank 2)

Exhaust Gas Recirculation (EGR)

Exhaust Gas Recirculation (EGR) codes will rarely cause any type of drive-ability issues. The EGR system is mainly present to reduce emissions (NOX). The EGR valve could be bad, lack of vacuum to the actuator, actuator could be bad, ports could be clogged.

Many vehicles are equipped with an EGR temp sensor that tells the computer the EGR valve has opened, that sensor could be bad. Many cars use the MAP sensor to tell if the EGR valve has opened, so if you have a vacuum leak or a faulty MAP sensor, you could get an EGR could in error.

Check your vacuum supplies, ensure the EGR valve opens, whether electric or vacuum opened, and dig into the theory of how this particular vehicle opens, and monitors the EGR valve.

P0400 Exhaust Gas Recirculation Flow Malfunction
P0401 Exhaust Gas Recirculation Flow Insufficient Detected
P0402 Exhaust Gas Recirculation Flow Excessive Detected
P0403 Exhaust Gas Recirculation Circuit Malfunction
P0404 Exhaust Gas Recirculation Circuit Range/Performance

Secondary Air

Secondary Air codes will rarely cause any type of drive-ability issues. The Secondary Air Injection system is mainly present to reduce emissions. Check to see that the air pump, whether belt driven or electric, is moving air, and that the air is getting to the exhaust. Very common problem on VW and Audi due to broken plastic tubes that direct the air. Could also be turned on in error due to a vacuum leak or a bad oxygen sensor.

P0410 Secondary Air Injection System Malfunction
P0411 Secondary Air Injection System Incorrect Flow Detected

Catalyst (Cat)

Catalyst (Cat) codes generally mean the cat has gone bad. Can be causes by a bad oxygen sensor, but that is generally not normally the case. Very hard to test a cat without shop equipment.

Bad cats will rarely have any symptoms, if they are plugged they will cause poor gas mileage, rough running, lack of power.

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)
P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)

Evaporative Emission Control System

Evaporative Emission Control System codes are generally hard to diagnose without shop equipment. Your best bet is to replace the gas cap and hope for the best. If the code comes back, you will need a smoke machine to properly find the leak. Any decent shop will have one.

P0440 Evaporative Emission Control System Malfunction
P0442 Evaporative Emission Control System Leak Detected (small leak)
P0455 Evaporative Emission Control System Leak Detected (gross leak)

Fuel Level

Fuel Level codes generally mean the fuel level sensor in the tank has gone bad.

P0460 Fuel Level Sensor Circuit Malfunction
P0461 Fuel Level Sensor Circuit Range/Performance
P0462 Fuel Level Sensor Circuit Low Input
P0463 Fuel Level Sensor Circuit High Input
P0464 Fuel Level Sensor Circuit Intermittent

Vehicle Speed

Vehicle Speed codes generally mean the sensor has gone bad.

P0500 Vehicle Speed Sensor Malfunction
P0501 Vehicle Speed Sensor Range/Performance
P0502 Vehicle Speed Sensor Low Input
P0503 Vehicle Speed Sensor Intermittent/Erratic/High

Idle Control System

Idle Control System codes – vacuum leak, failed idle air control (IAC) valve, dirty throttle body. Basically the vehicle has lost the ability to control the idle, either due to the idle control system failing, or some fort of gross fuel trim failure.

P0505 Idle Control System Malfunction
P0506 Idle Control System RPM Lower Than Expected
P0507 Idle Control System RPM Higher Than Expected

Transmission

Transmission codes are never a good sign. Short of a bad solenoid, or maybe a bad torque converter, you generally are due for a transmission rebuild if you have any transmission codes present. Check the fluid level, top off with the proper fluid if low.

P0730 Incorrect Gear Ratio
P0731 Gear I Incorrect ratio
P0732 Gear 2 Incorrect ratio
P0733 Gear 3 Incorrect ratio
P0734 Gear 4 Incorrect ratio
P0735 Gear 5 Incorrect ratio
P0736 Reverse incorrect gear ratio
P0740 Torque Converter Clutch Circuit Malfunction
P0741 Torque Converter Clutch Circuit Performance or Stuck Off
P0742 Torque Converter Clutch Circuit Stock On
P0743 Torque Converter Clutch Circuit Electrical
P0744 Torque Converter Clutch Circuit Intermittent
P0510 Closed Throttle Position Switch Malfunction

A quick note about oil changes. All good techs will clean the mating surface on the oil filter housing. Furthermore they will also lube the oil filter gasket with oil. Almost no techs I have met will pre-fill the oil filter. By filling the filter with oil, you are reducing the time it takes for the engine to achieve oil pressure. A minor detail, but a detail I wish more techs took the time to perform. If you are using BG’s MOA, it’s an easy solution to add the MOA to the filter.

Wet Oil Filter

So the next time you go in for an oil change, ask them for a “wet filter”. They should know what you want, and if they don’t, maybe you need a new mechanic.

A frequent cause of heartache for technicians, and car owners alike, is the failed E-test. Truth be told, just about any properly running vehicle will pass emission testing. This post will not be a laundry list of cheats. Rather, this post will be a comprehensive list of repair information, to aid in actually repairing the vehicle so it is in accordance with emission standards.

Pre-Test Tips

First and foremost, make sure your catalytic converter (cat) is hot before you go to emission testing. A cat is just a honeycomb of metal that becomes so hot it burns any left over fuel the motor was unable to burn. In order to incinerate the left-overs, the cat must become extremely hot.

The best way to ensure your cat is hot, is to cruise your car down the highway for 15 to 20 minutes before you go to test the vehicle. The exhaust temperature is the hottest during light throttle cruise. Running the car down the highway will heat soak the cat, to ensure it will “lite off” during testing.

A good old fashioned top end de-carb is always a good idea before emission testing a vehicle. If you can get a full injector purge, that is best. Simply adding BG’s 44k to the gas tank and sucking a bottle of de-carb through a vacuum line also works well. The carbon in a motor becomes hotter than the normal parts of the motor, which can lead to detonation, misfire, or high NOX due to elevated combustion chamber temperatures.

Check your cooling system. A faulty cooling system can cause pre-detonation, and high nox. Let your car cool down, and make sure the coolant is full. Low coolant levels can casue multiple problems. As recommended here replace your radiator cap every spring.

Catalytic Converter

Emission Failures – Rules of thumb:

Understanding emission fialures requires undersanding the 5 gases that result from internal combustion. The 5 gases we measuer are HC, CO, CO2, O2 and NOX.

5 Gas Analyzer Specifications at 2000 RPM extended hold, in neutral or park.

  • HC = 100 PPM or less
  • CO = Less than 0.3 %
  • CO2 = Over 13.5 %
  • O2 = Less than 1 %
  • NOX = 100 – 700
  • Lambda, will vary, depending on if you are under load.

Nox is a result of high combustion chamber temperatures.

Common causes of high nox are:

  • a lean condition
    • a vacuum leak
    • a failed O2 sensor
    • a failed MAF (mass air flow) sensor
    • a failed MAP (manifold absolute pressure) sensor
  • Incorrect timing; either ignition or camshaft / crankshaft sync
    • too much ignition timing (too advanced)
    • improper crankshaft/ camshaft timing
  • a faulty cooling system
    • a failed coolant temperature sensor
    • low coolant level
    • inoperable cooling fans
  • a failed EGR (exhaust gas recirculation) system
    • Failed EGR Valve
    • Failed EGR Valve Solenoid
    • Clogged EGR Ports
  • a failed secondary air system.
  • a failed catalytic converter
  • a high compression motor

HC is from unburned or partially burnt fuel.

HC is generally a sign of misfire, but can also be that the engine is just way too rich. Common causes of HC are:

  • a rich or lean misfire
    • a failed O2 sensor
    • a failed MAF sensor
    • a failed coolant temperature sensor
    • a vacuum leak
    • dirty or sticking injectors
  • an ignition misfire
    • old or faulty ignition parts (plugs, wires, coils)
    • improper crankshaft/ camshaft timing
    • Improper ignition timing
  • a failed catalytic converter
  • a failed secondary air system

** A fuel leak (even a fuel vapor leak) near the tail pipe can also cause HC failure. The machines that suck the exhaust in and test it will also suck in the raw fuel and cause a HC failure.

High CO occurs when a car is too rich.

Common causes include

  • a failed O2 sensor
  • a failed MAF sensor
  • a failed MAP (manifold absolute pressure) sensor
  • leaking or sticking injectors
  • a failed coolant temperature sensor
  • a fuel pressure regulator leaking fuel into the vacuum port
  • too little ignition timing
  • a failed catalytic converter
  • a failed secondary air system

O2 is an indicator of air fuel metering

An O2 level over 1% indicates a lean condition.

CO2 is an indicator of over all engine health.

If CO2 is not over 13.5 % you have a general engine performance problem. Low compresion, poor ignition, faulty air fuel metering or the like.

You’ve probably noticed a pattern here. Honestly, there are a handful of systems which keep the car running properly, and the emissions low. As long as all the systems are working properly, you should be fine, the trick is determining which systems have failed.

You have to look at all five gasses to get an idea of what is going on. For example, if NOX and HC are both high, CO are low, and the idle is too high, I’d check for a vacuum leak causing lean misfire. To really hone in on the problem, you will also need a proper scan tool to watch data streams, and a 5 gas analyzer.

Correcting Emission Failures

automotive repair scan tool

This is a relatively inexpensive scan tool made by autolink. It pulls codes as well as reads and displays your basic drive-ability data. I would recommend this to anyone who wants to repair any modern car (1996 or newer). I have one, and i use it all day long.

Check your easy stuff first. Plug in a scan tool and run through your basic data, engine coolant temperature, MAF grams per second, baro pressure, intake air temperature, etc. and make sure nothing is out to lunch. For example, is the coolant temperature stuck at 0 degrees Celsius, causing the vehicle to permanently stay in cold start enrichment?

Check the Air and Fuel Metering

Make sure your vehicle is in fuel control. Modern cars have two fuel control modes, closed loop and open loop. When the car is in open loop, it is simply running a pre-made map, and makes little to no changes to the amount of fuel it delivers. When a vehicle is in closed loop, it is closely monitoring the engine and adjusting fuel and timing to create the proper air fuel ratio, and a good clean burn.

Learn more about closed loop Vs. Open loop by understnading how check engien lights work.

Watch your front oxygen sensor/s. The sensors should switch back and forth between high and low values. Many oxygen sensors are one volt systems, and will therefore switch between .02 and .98 volts. Other systems are five volt, some are 1.5 volt. The main thing to look for is rapid switching (every second or so) between low and high values. If the oxygen sensor is switching, then the ECU (engine control unit) is adjusting fuel. If an oxygen sensor is switching slowly, or sticking at a value, then there is a gross failure in the fuel control system (MAF, engine coolant temperature sensor, Oxygen sensor, etc.)

If the car is equipped with a MAF, check to make sure it is clean. A dirty MAF can cause a lean condition.

If you have an old style MAF, such as this:

mass airflow sensor

You can actually open these old MAF’s up and tune them. They are a simple flapper door that swings open as the engine draws more air in. The main downfall of these early MAF’s is that the spring wears out. As the spring wears out, the door will open further than it should, and the car will run rich. Watch your five gas analyzer and adjust it one click at a time. If you don’t have a five gas, you can always adjust a few clicks and then run it back through emission testing, it’s just far more time consuming. Generally speaking, you will need to tighten the spring two or three clicks per 100,000 miles.

Look for Ignition Problems

If you have a distributor on the car, set your timing. Ignition timing that is too far advanced will result in high NOX. Ignition timing that is too far retarded may result in high HC or CO.

While you are at it, also inspect your spark plugs to ensure they are new. Always, make sure you have the proper spark plug in your vehicle. Teh factory spark plug is always the best spark plug. If you are not sure what plugs to use, get a set form the dealership.

You can sometimes find a faulty ignition system by soaking the engine with water. The water will make it easier for the ignition system to arc to ground rather than going through the spark plug. If your car has coil on plug ignition, you can stress test the coils by making them jump a gap before the spark plug.

Ingnition Tester

This is a tester you can put in line in your ignition system. By making the spark jump a gap, you can stress the ignition system and find a failing system. Very handy.

As a last ditch effort, you can also check and ensure the crankshaft/ camshaft timing is correct. I have heard rumor of a new timing belt bringing a NOX failure back in line, once, but that would be fairly rare.

Check Emission Specific Components

You can also test your cat to verify it is working properly. First, you can install a back pressure tester in a pre-cat oxygen sensor bung. Rev the motor while in park or neutral and ensure the back pressure is low enough. If the back pressure is too high, you car is plugged, and requires replacement. You can also watch the front and rear O2 sensors to get an idea if the cat is working.

Further more, watch your five gas analyzer to verify the cat is working. Watch the five gas as the car warms up. Once the cold start enrichment has leveled off, drive the vehicle and watch the emissions. Before the cat is hot enough to light off, you will see all the emissions the car produces. At a certain point, if the cat is working, you will see the emissions drop as soon as the cat lites off.

Check your EGR system (if equipped), which recirculates exhaust gas to lower combustion chamber temperatures, and mainly lower NOX. Most EGR valves are opened by engine vacuum and a solenoid. With the engine running, apply vacuum to the EGR valve. If the valve works and the ports are clear, the engine should stumble and die. If the engine remains running, you have a faulty EGR system. If the Valve holds vacuum, but the engine doesn’t die, the ports are most likely clogged. If the EGR valve doesn’t hold vacuum, the valve is most likely bad. Certainly, the valve can be bad AND you have clogged ports.

Similarly, check the vacuum supply going into the EGR solenoid. if the solenoid has proper engine vacuum going into it, check the power and ground at the solenoid. Also, supply power and ground to the solenoid with the engine running. If the solenoid works, it will open and send vacuum over to the EGR valve.

Also check your secondary air system, if equipped. Secondary air system pumps air into pre-cat exhaust to help the cat light off. If your secondary air pump is electric, power it up and check to make sure it flows air. If your air pump is mechanical, let the engine idle and check to see if the air pump works. Mechanical air pumps often also utilize a solenoid which opens when the secondary air is required. Power up this solenoid and ensure it is working.

See also: Check engine light causes.

This is a list of Generic trouble codes. To see manufacturer specific codes, click the name of the manufacturer.

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Acura Trouble Codes 1100-1199

P1106 BARO Sensor Circuit Range/Performance Malfunction
P1107 BARO Circuit Low Input
P1108 BARO Circuit High Input
P1121 Throttle Position Lower Than Expected
P1122 Throttle Position Higher Than Expected
P1128 MAP Lower Than Expected
P1129 MAP Higher Than Expected

Acura Trouble Codes 1200-1299

P1259 VTEC System Malfunction
P1297 ELD Circuit Low Input
P1298 ELD Circuit High Input

Acura Trouble Codes 1300-1399

P1300 Random Misfire
P1336 Crankshaft Speed Fluctuation Sensor Intermittant Interruption
P1337 Crankshaft Speed Fluctuation Sensor No Signal
P1359 Crankshaft Position/TDC/Cylinder Position Sensor Connector Disconnection
P1361 TDC Sensor Intermittent Interruption
P1362 TDC 1 Sensor No Signal
P1366 TDC 2 Sensor Intermittent
P1367 TDC 2 Sensor No Signal
P1381 Cylinder Position Sensor Intermittant Inturruption
P1382 Cylinder Position Sensor No Signal

Acura Trouble Codes 1400-1499

P1456 EVAP System Leak Detected (Fuel Tank System)
P1457 EVAP Control System Leak Detected (Control Canister System)
P1491 EGR Valve Lift Insufficient Detected
P1498 Voltage Problem In EGR Valve Position Sensor Circuit

Acura Trouble Codes 1500-1599

P1508 Idle Air Control Valve Circuit Failure
P1519 IAC Valve Circuit Failure

Acura Trouble Codes 1600-1699

P1607 ECM/PCM Internal Circuit Failure
P1656 Automatic Transaxle System Malfunction
P1660 A/T FI Data Line Failure
P1676 FPTDR Signal Line Failure
P1678 FPTDR Signal Line Failure
P1681 A/T FI Signal A Low Input
P1682 A/T FI Signal A High Input
P1686 A/T FI Signal B Low Input
P1687 A/T FI Signal B High Input

Acura Trouble Codes 1700-1799

P1705 Automatic Transaxle System Malfunction
P1706 Automatic Transaxle System Malfunction
P1709 Automatic Transaxle System Malfunction
P1710 Automatic Transaxle System Malfunction
P1713 Automatic Transaxle System Malfunction
P1738 Automatic Transaxle System Malfunction
P1739 Automatic Transaxle System Malfunction
P1740 Automatic Transaxle System Malfunction
P1753 Automatic Transaxle System Malfunction
P1758 Automatic Transaxle System Malfunction
P1768 Automatic Transaxle System Malfunction
P1773 Automatic Transaxle System Malfunction
P1778 Automatic Transaxle System Malfunction
P1786 Automatic Transaxle System Malfunction
P1790 Automatic Transaxle System Malfunction
P1791 Automatic Transaxle System Malfunction
P1792 Automatic Transaxle System Malfunction
P1794 Automatic Transaxle System Malfunction

Sometimes you just need to see it apart. Below is a list of links to pages with pictures of vehicles, all separated by make.

BMW Trouble Codes 1000-1099

P1083 Fuel Control Mixture Lean (Bank 1 Sensor 1)
P1084 Fuel Control Mixture Rich (Bank 1 Sensor 1)
P1085 Fuel Control Mixture Lean (Bank 2 Sensor 1)
P1086 Fuel Control Mixture Rich (Bank 2 Sensor 1)
P1087 O2 Sensor Circuit Slow Response in Lean Control Range (Bank 1 Sensor 1)
P1088 O2 Sensor Circuit Slow Response in Rich Control Range (Bank 1 Sensor 1)
P1089 O2 Sensor Circuit Slow Response in Lean Control Range (Bank 1 Sensor 2)
P1090 Pre-Catalyst Fuel Trim Too Lean Bank 1
P1091 Pre-Catalyst Fuel Trim Too Rich Bank 1
P1092 Pre-Catalyst Fuel Trim Too Lean Bank 2
P1093 Pre-Catalyst Fuel Trim Too Rich Bank 2
P1094 O2 Sensor Circuit Slow Response in Rich Control Range (Bank 2 Sensor 1)
P1095 O2 Sensor Circuit Slow Switching From Lean to Rich (Bank 1 Sensor 1)
P1096 O2 Sensor Circuit Slow Switching From Lean to Rich (Bank 2 Sensor 1)
P1097 O2 Sensor Circuit Slow Response after Coast Down Fuel Cutoff (Bank 1 Sensor 1)
P1098 O2 Sensor Circuit Slow Response after Coast Down Fuel Cutoff (Bank 2 Sensor 2)

BMW Trouble Codes 1100-1199

P1111 Engine Coolant Temperature Radiator Outlet Sensor Low Input
P1112 Engine Coolant Temperature Radiator Outlet Sensor High Input
P1115 Coolant Temperature Sensor Plausibility
P1116 Mass Or Volume Air Flow Circuit Range/Performance Problem (Bank 2)
P1117 Mass Or Volume Air Flow Circuit Low Input (Bank 2)
P1118 Mass Or Volume Air Flow Circuit High Input (Bank 2)
P1120 Pedal Position Sensor Circuit
P1121 Pedal Position 1 Range/Performance Problem
P1122 Pedal Position 1 Low Input
P1123 Pedal Position 1 High Input
P1132 O2 Sensor Heater Control Circuit (Bank 1 Sensor 1)
P1133 O2 Sensor Heater Control Circuit (Bank 2 Sensor 1)
P1134 O2 Sensor Heater Circuit Signal Intermittent (Bank 1 Sensor 2)
P1135 O2 Sensor Heater Circuit Low Voltage (Bank 1 Sensor 1)
P1136 O2 Sensor Heater Circuit High Voltage (Bank 1 Sensor 1)
P1137 O2 Sensor Heater Circuit Signal Intermittant (Bank 1 Sensor 2)
P1138 O2 Sensor Heater Circuit Low Voltage (Bank 1 Sensor 2)
P1139 O2 Sensor Heater Circuit High Voltage (Bank 1 Sensor 2)
P1140 Mass or Volume Air Flow Circuit Range/Performance Problem
P1145 Solenoid Valve Running Losses Control Circuit Electrical
P1151 O2 Sensor Heater Circuit Signal Intermittent (Bank 2 Sensor 1)
P1152 O2 Sensor Heater Circuit Low Voltage (Bank 2 Sensor 1)
P1153 O2 Sensor Heater Circuit High Voltage (Bank 2 Sensor 1)
P1155 O2 Sensor Heater Circuit Intermittent (Bank 2 Sensor 2)
P1156 O2 Sensor Heater Circuit Low Voltage (Bank 2 Sensor 2)
P1157 O2 Sensor Heater Circuit High Voltage (Bank 2 Sensor 2)
P1158 Fuel Trim Adaptive Bank 1 Low
P1159 Fuel Trim Adaptive Bank 1 High
P1160 Fuel Trim Adaptive Bank 2 Low
P1161 Fuel Trim Adaptive Bank 2 High
P1162 Fuel Trim Adaptive Per Ignition Bank 1 Low
P1163 Fuel Trim Adaptive Per Ignition Bank 1 High
P1164 Fuel Trim Adaptive Per Ignition Bank 2 Low
P1165 Fuel Trim Adaptive Per Ignition Bank 2 High
P1174 Fuel Trim Adaptation Bank 1 Malfunction
P1175 Fuel Trim Adaptation Bank 2 Malfunction
P1176 O2 Sensor Slow Response Bank 1
P1177 O2 Sensor Slow Response Bank 2
P1178 O2 Sensor Signal Circuit Slow Switching From Rich to Lean (Bank 1 Sensor 1)
P1179 O2 Sensor Signal Circuit Slow Switching From Rich to Lean (Bank 2 Sensor 1)
P1180 O2 Sensor Signal Circuit Slow Switching From Rich to Lean (Bank 1 Sensor 2)
P1181 O2 Sensor Signal Circuit Slow Switching From Rich to Lean (Bank 2 Sensor 2)
P1182 O2 Sensor (Bank 1 Sensor 2) Open Circuit During Coast Down Fuel Cut-off
P1183 O2 Sensor (Bank 2 Sensor 2) Open Circuit During Coast Down Fuel Cut-off
P1186 O2 Sensor Heater Control Circuit (Bank 1 Sensor 2)
P1187 O2 Sensor Heater Control Circuit (Bank 2 Sensor 2)
P1188 Fuel Control (Bank 1 Sensor 1)
P1189 Fuel Control (Bank 2 Sensor 1)
P1190 Pre-catalyst Fuel Trim System Bank 1
P1191 Pre-catalyst Fuel Trim System Bank 2
P1192 Post-catalyst Fuel Trim System Bank 1
P1193 Post-catalyst Fuel Trim System Bank 2

BMW Trouble Codes 1200-1299

P1221 Pedal Position Sensor 2 Range/Performance Problem
P1222 Pedal Position Sensor 2 Low Input
P1223 Pedal Position Sensor 2 High Input
P1270 Control Module Self-Test, Torque Monitoring
P1271 Ambient Air Pressure Sensor Electrical
P1283 Switching Solenoid for Air Assisted Injection Valves Bank 1 Control Circuit Electrical
P1284 Switching Solenoid for Air Assisted Injection Valves Bank 1 Control Circuit Signal Low
P1285 Switching Solenoid for Air Assisted Injection Valves Bank 1 Control Circuit Signal High
P1287 Switching Solenoid for Air Assisted Injection Valves Bank 2 Control Circuit Electrical
P1288 Switching Solenoid for Air Assisted Injection Valves Bank 2 Control Circuit Signal Low
P1289 Switching Solenoid for Air Assisted Injection Valves Bank 2 Control Circuit Signal High

BMW Trouble Codes 1300-1399

P1313 “A” Camshaft Position Plausibility
P1317 “B” Camshaft Position Plausibility
P1327 Knock Sensor 2 (Bank 1) Low Input
P1328 Knock Sensor 2 (Bank 1) High Input
P1332 Knock Sensor 4 Low Input
P1333 Knock Sensor 4 High Input
P1340 Multiple Cylinder Misfire During Start
P1341 Multiple Cylinder Misfire With Fuel Cut-off
P1342 Misfire During Start Cylinder 1
P1343 Misfire Cylinder 1 With Fuel Cut-off
P1344 Misfire During Start Cylinder 2
P1345 Misfire Cylinder 2 With Fuel Cut-off
P1346 Misfire During Start Cylinder 3
P1347 Misfire Cylinder 3 With Fuel Cut-off
P1348 Misfire During Start Cylinder 4
P1349 Misfire Cylinder 4 With Fuel Cut-off
P1350 Misfire During Start Cylinder 5
P1351 Misfire Cylinder 5 With Fuel Cut-off
P1352 Misfire During Start Cylinder 6
P1353 Misfire Cylinder 6 With Fuel Cut-off
P1354 Misfire During Start Cylinder 7
P1355 Misfire Cylinder 7 With Fuel Cut-off
P1356 Misfire During Start Cylinder 8
P1357 Misfire Cylinder 8 With Fuel Cut-off
P1358 Misfire During Start Cylinder 9
P1359 Misfire Cylinder 9 With Fuel Cut-off
P1360 Misfire During Start Cylinder 10
P1361 Misfire Cylinder 10 With Fuel Cut-off
P1362 Misfire During Start Cylinder 11
P1363 Misfire Cylinder 11 With Fuel Cut-off
P1364 Misfire During Start Cylinder 12
P1365 Misfire Cylinder 12 With Fuel Cut-off
P1384 Knock Sensor 3 Circuit
P1385 Knock Sensor 4 Circuit
P1386 Control Module Self-test, Knock Control Baseline Test Bank 1
P1396 Crankshaft Position Sensor Segment Timing Plausibility
P1397 Camshaft Position Sensor “B” Circuit (Bank 1)

BMW Trouble Codes 1400-1499

P1400 Heated Catalyst Battery Voltage or Current too Low During Heating (Bank 1)
P1401 Heated Catalyst Current too High During Heating (Bank 1)
P1402 Heated Catalyst Power Switch Overtemperature Condition (Bank 1)
P1403 Carbon Canister Shut Off valve Control Circuit Electrical
P1404 Heated Catalyst Current too High During Heating (Bank 2)
P1405 Heated Catalyst Power Switch Overtemperature Condition (Bank 2)
P1406 Heated Catalyst Internal Control Module Checksum/ROM Error
P1413 Secondary Air Injection Pump Relay Control Circuit Signal Low
P1414 Secondary Air Injection System Monitor Circuit High
P1420 Secondary Air Valve Control Circuit Electrical
P1421 Secondary Air System Bank 1
P1422 Secondary Air System Bank 2
P1432 Secondary Air Injection System Incorrect Flow Detected
P1438 Purge Control Valve Control Open Circuit
P1439 Purge Control Valve Control Circuit Signal Low
P1440 Purge Control Valve Control Circuit Signal High
P1441 Leakage Diagnostic Pump Control Open Circuit
P1442 Leakage Diagnostic Pump Control Circuit Signal Low
P1443 Leakage Diagnostic Pump Control Circuit Signal High
P1444 Diagnostic Module Tank Leakage (DM-TL) Pump Control Open Circuit
P1445 Diagnostic Module Tank Leakage (DM-TL) Pump Control Circuit Signal Low
P1446 Diagnostic Module Tank Leakage (DM-TL) Pump Control Circuit Signal High
P1447 Diagnostic Module Tank Leakage (DM-TL) Pump Too High During Switching
P1448 Diagnostic Module Tank Leakage (DM-TL) Pump Too Low During Switching
P1449 Diagnostic Module Tank Leakage (DM-TL) Pump Too High
P1450 Diagnostic Module Tank Leakage (DM-TL) Switching Solenoid Open Circuit
P1451 Diagnostic Module Tank Leakage (DM-TL) Switching Solenoid Control Circuit Signal Low
P1452 Diagnostic Module Tank Leakage (DM-TL) Switching Solenoid Control Circuit Signal High
P1453 Secondary Air Injection Pump Relay Control Circuit Electrical
P1454 Secondary Air Injection Pump With Series Resistor Control Circuit Electrical
P1456 Heated Catalyst Heater Power Supply Open Circuit (Bank 1)
P1457 Heated Catalyst Heater Power Switch Temperature Sensor Electrical (Bank 1)
P1459 Heated Catalyst Heater Power Supply Open Circuit (Bank 2)
P1460 Heated Catalyst Heater Power Switch Temperature Sensor Electrical (Bank 2)
P1461 Heated Catalyst Gate Voltage Signal Low
P1462 Heated Catalyst Internal Control Module Checksum/ROM Error
P1463 Heated Catalyst Battery Temperature Sensor 1 Electrical
P1464 Heated Catalyst Battery Temperature Sensor 2 Electrical
P1465 Heated Catalyst Battery Temperature Sensor 1 or 2 Plausibility
P1466 Heated Catalyst Power Switch Temperature Sensor Plausibility
P1467 Heated Catalyst Comparison Battery Voltages of Power Switches Plausibility
P1468 Heated Catalyst Battery Disconnecting Switch Plausibility
P1470 Leakage Diagnostic Pump Control Circuit Electrical
P1472 Diagnostic Module Tank leakage (DM-TL) Switching Solenoid Control Circuit Electrical
P1473 Diagnostic Module Tank leakage (DM-TL) Pump Current Plausibility
P1475 Leakage Diagnostic Pump Reed Switch Did Not Close
P1476 Leakage Diagnostic Pump Clamped Tube
P1477 Leakage Diagnostic Pump Reed Switch Did Not Open

BMW Trouble Codes 1500-1599

P1500 Idle Speed Control Valve Stuck Open
P1501 Idle Speed Control Valve Stuck Closed
P1502 Idle Speed Control Valve Closing Solenoid Control Circuit Signal High or Low
P1503 Idle Speed Control Valve Closing Solenoid Control Circuit Signal Low
P1504 Idle Speed Control Valve Closing Solenoid Control Open Circuit
P1505 Idle Speed Control Valve Closing Solenoid Control Circuit Electrial
P1506 Idle Speed Control Valve Open Solenoid Control Circuit Signal High
P1507 Idle Speed Control Valve Open Solenoid Control Circuit Signal Low
P1508 Idle Speed Control Valve Opening Solenoid Control Open Circuit
P1509 Idle Speed Control Valve Opening Solenoid Control Circuit Electrical
P1510 Idle Speed Control Valve Stuck
P1511 DISA Control Circuit Electrical
P1512 DISA Control Circuit Signal Low
P1513 DISA Control Circuit Signal High
P1519 “A” Camshaft Position Actuator Bank 1
P1520 “B” Camshaft Position Actuator Bank 1
P1522 “A” Camshaft Position Actuator Bank 2
P1523 “A” Camshaft Position Actuator Signal Low Bank 1
P1524 “A” Camshaft Position Actuator Signal High Bank 1
P1525 “A” Camshaft Position Actuator Control Open Circuit Bank 1
P1526 “A” Camshaft Position Actuator Control Open Circuit Bank 2
P1527 “A” Camshaft Position Actuator Control Circuit Signal Low Bank 1
P1528 “A” Camshaft Position Actuator Control Circuit Signal High Bank 1
P1529 “B” Camshaft Position Actuator Control Circuit Signal Low Bank 1
P1530 “B” Camshaft Position Actuator Control Circuit Signal High Bank 1
P1531 “B” Camshaft Position Actuator Control Open Circuit Bank 1
P1532 “B” Camshaft Position Actuator Control Open Circuit Bank 2
P1533 “B” Camshaft Position Actuator Control Circuit Signal Low Bank 2
P1534 “B” Camshaft Position Actuator Control Circuit Signal High Bank 2
P1540 Pedal Position Sensor
P1541 Pedal Position Sensor Double Error
P1542 Pedal Position Sensor Electrical
P1543 Pedal Position Sensor
P1544 Pedal Position Sensor
P1545 Pedal Position Sensor
P1546 Pedal Position Sensor
P1550 Idle Speed Control valve Closing Solenoid Control Circuit Electrical
P1551 “A” Camshaft Position Actuator Control Open Circuit Bank 1
P1552 “A” Camshaft Position Actuator Control Open Circuit Bank 1
P1556 “A” Camshaft Position Actuator Control Open Circuit Bank 1
P1560 “B” Camshaft Position Actuator Control Open Circuit Bank 1
P1564 Control Module Selection
P1565 “B” Camshaft Position Actuator Control Open Circuit Bank 1
P1569 “A” Camshaft Position Actuator Control Open Circuit Bank 2
P1580 Throttle Valve Mechanically Stuck
P1581 “B” Camshaft Position Actuator Control Open Circuit Bank 2
P1589 Control Module Self Test, Knock Control Test Pulse Bank 1
P1593 DISA Control Circuit Electrical
P1594 “B” Camshaft Position Actuator Control Open Circuit Bank 2

BMW Trouble Codes 1600-1699

P1602 Control Module Self Test, Control Module Defective
P1603 Control Module Self Test, Torque Monitoring
P1604 Control Module Self Test, Speed Monitoring
P1607 CAN Version
P1608 Serial Communicating Link Control Module
P1609 Serial Communicating Link EML
P1611 Serial Communicating Link Transmission Control Module
P1619 MAP Cooling Control Circuit Signal Low
P1620 MAP Cooling Control Circuit Signal High
P1622 MAP Cooling Control Circuit Electrical
P1623 Pedal Position Sensor Potentiometer Supply
P1624 Pedal Position Sensor Potentiometer Supply Channel 1 Electrical
P1625 Pedal Position Sensor Potentiometer Supply Channel 2 Electrical
P1632 Throttle Valve Adaptation; Adaptation Condition Not Met
P1633 Throttle Valve Adaptation; Limp Home Position
P1634 Throttle Valve Adaptation; Spring Test Failed
P1635 Throttle Valve Adaptation; Lower Mechanical Stop Not Adapted
P1636 Throttle Valve Control Circuit
P1637 Throttle Valve Position Control; Control Deviation
P1638 Throttle Valve Position Control; Throttle Stuck Temporarily
P1639 Throttle Valve Position Control; Throttle Stuck Permanently
P1640 Internal Control Module (ROM/RAM) Error
P1690 Malfunction Indicator Lamp (MIL) Electrical

BMW Trouble Codes 1700-1799

P1734 Pressure Control Solenoid “B” Electrical
P1738 Pressure Control Solenoid “C” Electrical
P1743 Pressure Control Solenoid “E” Electrical
P1744 Pressure Control Solenoid “A” Electrical
P1746 Transmission Control Module Output Stage
P1747 CAN Bus Monitoring
P1748 Transmission Control Module Self Test
P1749 Secondary Pressure Solenoid Communication Error
P1750 Secondary Pressure Solenoid Circuit Range/Performance
P1751 Secondary Pressure Solenoid Open Circuit
P1761 Shift Solenoid Malfunction
P1765 CAN Throttle Valve
P1770 CAN Torque Interface
P1780 CAN Torque Reduction