All OBD2 Fault Codes
What are OBD2 fault codes?
These codes form part of the diagnostic system in modern automobiles that inform you of problems. You (or a trained mechanic) can use these to quickly find the root of any issues that your car may be experiencing, saving massive amounts of time.
These codes can cover everything from the exhaust system all the way through to the air-conditioning and can be detected using an OBD2 scanner.
An OBD2 scanner can be bought very cheaply thanks to advancements in technology and typically look like the device to the right of this text.
Some solutions that are available are even smaller and use Bluetooth to transmit the error code to a mobile device (smartphone etc.).
They usually only present a 5-character code to the user - to decrypt this you will need to use this website to find a plain-English explanation.
Which fault codes are the most common?
With most modern cars you will find its the same problems occuring from normal day-to-day driving and so these following codes are more likely to appear on your reader.
P0010
Intake Camshaft Position Actuator Circuit / Open (Bank 1)
This fault is linked to the camshaft and is usually caused by (best-case scenario) dirty engine oil clogging up the mechanism. The ECU detects a problem with the camshaft timing sensor in the engine and displays the P0010 error code.
Read More About P0010 P0011
Intake Camshaft Position Timing - Over-Advanced (Bank 1)
Another camshaft error possibly caused by dirty engine oil, the P0011 fault code signifies a problem with timing in that part of the engine. Failing to sort this out could lead to misfires and potentially engine damage leading to an expensive replacement.
Read More About P0011 P0012
Intake Camshaft Position Timing - Over-Retarded (Bank 1)
When your car's ECU presents you with the P0012 fault code it is showing you that it is seeing an issue with the camshaft timing. This is most commonly caused by a low level of or dirty oil but can also be a sign of trouble in another component in the timing system.
Read More About P0012 P0013
Exhaust Camshaft Position Actuator Circuit / Open (Bank 1)
Leading away from the camshaft and to the exhaust you have an actuator for a valve that can open/close to control noise (or power in a VVT engine). A P0013 fault code suggests something is wrong with this component or the sensor attached to it.
Read More About P0013 P0014
Exhaust Camshaft Position Timing - Over-Advanced (Bank 1)
On vehicles that feature variable valve timing technology, you could find a P0014 fault code appearing. This is to inform you that the camshaft timing is out of sync and further damage could be caused if you continue to run the engine.
Read More About P0014 P0016
Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
If you are shown the P0016 fault code on your reader then the car you are working on is suffering from a timing issue. This may be caused by dirty oil or contaminants but also could be down to a stretched timing belt/chain.
Read More About P0016 P0017
Crankshaft Position Camshaft Position Correlation Bank 1 Sensor B
The P0017 fault code refers to the detection of a misalignment in the sensors monitoring the position of the camshaft. It could be fixed by a simple oil change but could go as far as being caused by a stretched timing belt or faulty solenoids.
Read More About P0017 P0036
Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 1 Sensor 2
A P0036 fault code is telling you that the level of oxygen in the exhaust is higher than it should be. The cause of this could be just a dirty air filter but could be a symptom of a bigger problem such as a leaking intake manifold.
Read More About P0036 P0102
Mass or Volume Air Flow Circuit Low Voltage Input
A P0102 suggests that the engine in the car is not receiving enough air according to the mass air flow sensor. This could be down to a dirty air filter restricting the flow of air or even a problem with the sensor itself or its connections.
Read More About P0102 P0106
Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
A P0106 fault code is telling you that the air pressure in the intake manifold is outside of the normal range. This could be a sign of a serious problem as the air/fuel mixture could be leaking and so running the engine with this code can be dangerous.
Read More About P0106 P0113
Intake Air Temperature Circuit High Input
The intake air temperature sensor has detected that the levels it deems as normal have been breached when the fault code P0113 is present. This could be down to a faulty part or connection or a symptom of a bigger problem in the engine.
Read More About P0113 P0128
Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)
If the P0128 fault code is displayed on your OBD2 reader then the car you are working on has probably got a low level of coolant. If that isn't the case then the cooling fan may not be working properly when the car is running or a sensor is faulty.
Read More About P0128 P0131
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
A P0131 fault code is showing you that the oxygen sensor 1 at bank 1 is reading a dangerous level. This is also called the fuel/air sensor and works by measuring the change of resistance in a piece of wire in the pipe before the catalytic converter.
Read More About P0131 P0134
O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)
Seeing a P0134 fault code appear is how your ECU is telling you that there is a problem with the oxygen sensor in the pipe that leaves your engine and heads toward the catalytic converter. It is not seeing an expected change in readings when operating.
Read More About P0134 P0135
O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
The P0135 code could be telling you that either the oxygen sensor (in the pipe that travels from the engine to the catalytic converter) is faulty or is experiencing an unusually high level of resistance - most commonly an error.
Read More About P0135 P0137
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
The P0137 error code is signalling that the 2nd fuel/air sensor (after the catalytic converter) is experiencing a lower voltage than is expected. This could be down to a faulty sensor or a problem in the catalytic converter or even further back to the engine.
Read More About P0137 P0138
O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
Like the P0137 error, the P0138 suggests that there is an over-voltage at the 2nd air/fuel sensor that is in play after the catalytic converter. It can be caused by a problem with the sensor or if working then a problem up-stream towards the engine.
Read More About P0138 P0141
O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
Your ECU tests many sensors during the startup of the car and if it detects that the oxygen sensor after the catalytic converter is out of voltage range then it will display the P0141 fault code when an OBD2 reader is plugged in.
Read More About P0141 P0171
System Too Lean (Bank 1)
During the running of the engine, a P0171 fault code signals that the air/fuel mix is too lean (too much air or not enough fuel). This could be a sign that there is a leak somewhere or even that the sensor itself is no longer working.
Read More About P0171 P0172
System Too Rich (Bank 1)
Much like the P0171 error code, the P0172 signals the opposite. A P0172 code suggests that the engine is running too rich with a much too high level of fuel with not enough air entering the engine at the mass flow sensor.
Read More About P0172 P0175
System Too Rich (Bank 2)
P0175 signifies that the fuel/air mix that is entering the engine through the mass air flow sensor is too rich along the second bank. The 2nd bank is only applicable to engines with more than 1 row of pistons such as a V6.
Read More About P0175 P0300
Random/Multiple Cylinder Misfire Detected
Seeing a P0300 error code on your OBD2 reader suggests that the ECM is seeing misfiring across random or all of the cylinders in the engine. This is most likely caused by a lack of fuel entering into the engine in the fuel/air mix.
Read More About P0300 P0301
Cylinder 1 Misfire Detected
The P0301 is similar to the P0300 error but more isn't as random - it signals that there is a misfire in cylinder 1. This is most likely a lack of fuel reaching the cylinder or a faulty spark plug not igniting the mix correctly.
Read More About P0301 P0302
Cylinder 2 Misfire Detected
The P0302 code is the ECM telling you that the 2nd cylinder in the engine is experiencing a misfire. Unlike the "random" P0300 error code this one tells you that the issue is only in one cylinder and probably a faulty spark plug.
Read More About P0302 P0303
Cylinder 3 Misfire Detected
P0303 is telling you that there is a problem with the third cylinder of your engine. The ECM is experiencing a misfire in that cylinder alone because the fuel/air mix isn't igniting properly - most commonly this is a spark plug issue.
Read More About P0303 P0304
Cylinder 4 Misfire Detected
Replacing your spark plug in the 4th cylinder of your engine could be the most simple fix for the P0304 error code. This code is your ECM trying to tell you that a misfire is being caused in that cylinder along.
Read More About P0304 P0305
Cylinder 5 Misfire Detected
A P0305 fault code is centralized to just the 5th cylinder in your engine. It is the ECM telling you that a misfire is taking place and this probably build down to the spark plug not doing its job properly and needs to be replaced.
Read More About P0305 P0306
Cylinder 6 Misfire Detected
Replacing the spark plug in the 6th cylinder of your engine could be the easiest fix for the P0306 fault code. This is because your engine is experiencing a misfire in that chamber alone by throwing up this code suggesting all others are OK.
Read More About P0306 P0325
Knock Sensor 1 Circuit (Bank 2 or Single Sensor)
A P0325 code suggests that there is a triggering of the "knock sensor" in your engine. This "knocking" is caused by the fuel/air mix igniting too early and leads to a loss of power and increased pollutants exiting through the exit.
Read More About P0325 P0449
Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
Read More About P0449