Introduction
Since 1996, all vehicles have been equipped with the OBD2 system, an evolution of the OBD system implemented in California in 1991 to reduce atmospheric pollutant emissions. The OBD2 system adds two oxygen sensors, one before and one after the catalytic converter, to check its correct operation. The OBD I system already incorporated controllers for different systems and components related to gas emissions.
A crucial part of OBD mandates that vehicles have a malfunction indicator light, called the MIL (Malfunction Indicator Lamp), represented in various ways, from an engine image to texts like “Check Engine” or “Service Engine Soon.” This compilation of descriptions, explanations, causes, symptoms, and solutions is designed to assist mechanics in vehicle repairs and is the result of research across different media, including electronic resources. It covers over 100 of the most frequently consulted OBD2 fault codes at e-auto.com.mx. In some cases, links to videos or online materials are included to better understand the operation of different sensors and the tests performed on them, leveraging various resources to help you repair vehicles in your workshop. We sincerely hope this manual is a great help to you.
Created in August 2011
Index of Common OBD2 Codes
| CODE | PAGE | CODE | PAGE | CODE | PAGE | CODE | PAGE |
|---|---|---|---|---|---|---|---|
| P0010 | 1 | P0135 | 22 | P0208 | 49 | P0306 | 58 |
| P0011 | 1 | P0136 | 22 | P0209 | 50 | P0307 | 59 |
| P0020 | 2 | P0137 | 23 | P0210 | 51 | P0308 | 59 |
| P0021 | 2 | P0138 | 23 | P0211 | 52 | P0309 | 60 |
| P0031 | 3 | P0139 | 24 | P0212 | 53 | P0310 | 60 |
| P0032 | 4 | P0140 | 25 | P0217 | 54 | P0311 | 61 |
| P0051 | 5 | P0141 | 26 | P0230 | 54 | P0312 | 61 |
| P0052 | 6 | P0150 | 27 | P0231 | 55 | P0325 | 62 |
| P0100 | 7 | P0151 | 28 | P0300 | 55 | P0340 | 62 |
| P0101 | 8 | P0153 | 29 | P0301 | 56 | P0341 | 63 |
| P0102 | 9 | P0155 | 29 | P0302 | 56 | P0400 | 64 |
| P0103 | 10 | P0156 | 30 | P0303 | 57 | P0401 | 65 |
| P0104 | 11 | P0159 | 30 | P0304 | 57 | P0402 | 65 |
| P0106 | 11 | P0161 | 31 | P0305 | 58 | P0403 | 66 |
| P0107 | 12 | P0171 | 31 | P0410 | 67 | P0420 | 68 |
| P0108 | 12 | P0172 | 32 | P0421 | 68 | P0430 | 69 |
| P0109 | 13 | P0174 | 32 | P0431 | 69 | P0440 | 70 |
| P0112 | 13 | P0175 | 33 | P0440 | 70 | P0441 | 70 |
| P0113 | 14 | P0176 | 34 | P0441 | 70 | P0442 | 71 |
| P0117 | 14 | P0180 | 34 | P0442 | 71 | P0443 | 72 |
| P0118 | 15 | P0181 | 35 | P0443 | 72 | P0446 | 73 |
| P0121 | 15 | P0182 | 35 | P0446 | 73 | P0453 | 74 |
| P0122 | 16 | P0183 | 36 | P0453 | 74 | P0455 | 75 |
| P0123 | 16 | P0186 | 36 | P0455 | 75 | P0456 | 75 |
| P0125 | 17 | P0187 | 37 | P0456 | 75 | P0500 | 76 |
| P0127 | 17 | P0188 | 37 | P0500 | 76 | P0501 | 76 |
| P0128 | 18 | P0190 | 38 | P0501 | 76 | P0506 | 77 |
| P0130 | 19 | P0191 | 39 | P0506 | 77 | P0507 | 77 |
| P0131 | 20 | P0192 | 40 | P0507 | 77 | P0601 | 78 |
| P0132 | 20 | P0193 | 41 | P0601 | 78 | P0603 | 78 |
| P0133 | 21 | P0201 | 42 | P0603 | 78 | ||
| P0134 | 21 | P0202 | 43 |
Common OBD2 Codes: Descriptions, Causes, and Solutions
P0010 – “A” Camshaft Position Actuator Circuit (Bank 1)
Description: This OBD-II trouble code indicates a problem with the camshaft position actuator circuit for bank 1.
Explanation: Code P0010 refers to the oil control valve solenoid of the VVT (Variable Valve Timing) or VCT (Variable Camshaft Timing) system, its components, and the PCM. This code means the voltage in the circuit has dropped below a threshold set by the manufacturer for a specific time.
Symptoms:
- MIL (Malfunction Indicator Lamp) is on.
- Difficulty starting the engine.
- Rough engine idling.
Possible Causes:
- Defective Oil Control Valve (OCV).
- Open or short circuit in the VVT/VCT circuit.
- Damaged PCM (Powertrain Control Module).
Possible Solutions:
- Carefully check the Bank 1 VVT/VCT circuit, wiring system, and connectors as indicated in the repair manual.
- With the engine warm, check the operation of the OCV; replace or repair as necessary.
More Information:
Video of CMP Sensor (Example Link – Replace with relevant English video if possible)
Alt text: Diagram of a Camshaft Position Sensor (CMP) location in an engine, highlighting its role in variable valve timing systems.
P0011 – “A” Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)
Description: This OBD-II code signals an issue with the camshaft timing being too advanced or a performance problem in bank 1.
Explanation: Code P0011 is related to the VVT (Variable Valve Timing) or VCT (Variable Camshaft Timing) system, its components, and the PCM (also known as ECM – Engine Control Module). While the system comprises several components, P0011 specifically points to the camshaft timing. In this case, if the cam timing is beyond a set limit (over-advanced), the MIL will illuminate, and the code will be set.
Symptoms:
- Hard starting.
- Rough idle.
Possible Causes:
- Incorrect camshaft timing.
- Timing control valve solenoid issue (stuck open).
- Continuous oil flow to the VCT piston chamber.
- Wiring problems (wiring and/or connectors).
Possible Solutions:
- This fault code usually results from a mechanical failure in the VCT unit or related components, reducing the need for electrical diagnosis. Consult the vehicle’s repair manual for component tests for the VCT unit.
More Information:
Video of CMP Sensor (Example Link – Replace with relevant English video if possible)
Video of VVT System (Example Link – Replace with relevant English video if possible)
Alt text: Illustration of a Variable Valve Timing (VVT) system, showing the mechanism and components involved in adjusting camshaft timing for engine performance.
P0020 – “A” Camshaft Position Actuator Circuit (Bank 2)
Description: This OBD-II trouble code is similar to P0010 but applies to bank 2, indicating a fault in the camshaft position actuator circuit.
Explanation: Code P0020 is analogous to P0010, referring to the oil control valve (solenoid valve) of the VVT (Variable Valve Timing) or VCT (Variable Camshaft Timing) system, components, and PCM, but for Bank 2. This code indicates that the voltage in the circuit for bank 2 has dropped below a specified limit for a certain duration. Bank 2 refers to the engine side that does not contain cylinder #1.
Symptoms:
- MIL (Malfunction Indicator Lamp) is on.
- Rough engine idle.
- Other symptoms may be present.
Possible Causes:
- Defective Oil Control Valve (OCV) for Bank 2.
- Open or short circuit in the Bank 2 VVT/VCT circuit.
- Damaged PCM.
Possible Solutions:
- Carefully inspect the Bank 2 VVT/VCT circuit, wiring, and connectors, as detailed in the repair manual.
- With the engine at operating temperature, check the OCV operation, replacing or repairing as necessary.
More Information:
Video of CMP Sensor (Example Link – Replace with relevant English video if possible)
Video of VVT System (Example Link – Replace with relevant English video if possible)
P0021 – “A” Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)
Description: Similar to P0011, this code indicates over-advanced camshaft timing or system performance issues, but for bank 2.
Explanation: Code P0021 mirrors P0011, relating to the VVT (Variable Valve Timing) or VCT (Variable Camshaft Timing) system and the ECM, but for Bank 2. If the camshaft timing for bank 2 is over-advanced beyond a set limit, the MIL will illuminate, and this code will be registered. This code is essentially the same as P0011, except it pertains to bank 2 of the engine.
Symptoms:
- Hard starting.
- Rough idle.
- MIL (Malfunction Indicator Lamp) is on.
Possible Causes:
- Incorrect camshaft timing.
- Faulty timing control valve solenoid (stuck or open).
- Continuous oil flow to the VCT piston chamber.
- Wiring problems (wiring and/or connectors).
Possible Solutions:
- This fault code typically arises from a mechanical failure of the VCT unit or related components, minimizing the need for electrical diagnosis. Refer to the specific vehicle repair manual for component testing procedures for the VCT unit on Bank 2.
More Information:
Video of CMP Sensor (Example Link – Replace with relevant English video if possible)
Video of VVT System (Example Link – Replace with relevant English video if possible)
P0031 – Heated Oxygen Sensor (HO2S) Heater Control Circuit Low (Bank 1 Sensor 1)
Description: This OBD-II code indicates a low voltage in the heater control circuit for the upstream oxygen sensor in bank 1.
Explanation: Code P0031 pertains to the oxygen sensor located in Bank 1, upstream of the catalytic converter. Sensor #2 is positioned downstream of the converter. This upstream oxygen sensor (Sensor #1) is sometimes referred to as an air-fuel ratio sensor, as it measures the oxygen content in the exhaust gases relative to ambient air. This data is used by the vehicle’s computer to adjust the air-fuel mixture in the cylinders. Oxygen sensors are less efficient at lower exhaust gas temperatures. Therefore, some are equipped with a heater activated to ensure accurate readings, known as wideband sensors. P0031 indicates that the resistance in the heater circuit is lower than normal. Typically, resistance must fall below 0.8 Amperes to trigger this fault code. This code is similar to P0032, P0051, and P0052.
Symptoms:
- MIL (Malfunction Indicator Lamp) is on.
Possible Causes:
- Short or open circuit in the sensor heater circuit.
- Damaged wiring/connectors leading to the sensors and/or faulty relay.
- Faulty PCM.
Possible Solutions:
- Inspect the wiring and connectors leading to the sensor. Use a digital multimeter to check for continuity and shorts.
- If the system includes a relay and fuse, check these components.
- Verify 12 volts at the heater circuit power supply (disconnect the sensor for this measurement).
- Measure the resistance of the heater circuit (at the sensor itself).
- Measure wire resistance and voltage.
- Consult a service manual for correct voltage and resistance specifications for your vehicle.
- A common solution for P0031 is replacing the Bank 1 Sensor 1 oxygen sensor.
More Information:
Video and Information on Oxygen Sensors (Example Link – Replace with relevant English video if possible)
Alt text: Diagram of an Oxygen Sensor, illustrating its components and placement in the exhaust system to monitor oxygen levels for emissions control.
P0032 – Heated Oxygen Sensor (HO2S) Heater Control Circuit High (Bank 1 Sensor 1)
Description: This OBD-II code signals a high voltage condition in the heater control circuit for the upstream oxygen sensor in bank 1.
Explanation: Fault code P0032 is related to the oxygen sensor located in Bank 1, before the catalytic converter. A second oxygen sensor is located after the converter. This Sensor #1 oxygen sensor may also be referred to as an air/fuel ratio sensor as, in some vehicles, it detects the amount of oxygen in the exhaust gases compared to the outside air. This information is used by the vehicle’s computer to adjust the air/fuel ratio in the cylinder. The sensor is less effective when the exhaust gas temperature is low, so in some cases, it is equipped with a heater that is activated to obtain better readings. Code P0032 means that the resistance of the heater circuit is higher than normal. In most cases, this resistance level must be above 10 Amps to activate the fault code. This code is very similar in nature to codes P0031, P0051, and P0052.
Symptoms:
- MIL (Malfunction Indicator Lamp) is on.
Possible Causes:
- Short or open circuit in the sensor heater circuit.
- Faulty heater sensor.
- Damaged wiring/connectors leading to the sensors and/or faulty relay.
- Faulty PCM.
Possible Solutions:
- Check the wiring and connectors leading to the sensor.
- If the system includes a relay and a fuse, check them.
- Verify 12 volts in the heater circuit power supply (disconnect the sensor to make this measurement).
- Measure the resistance of the heater circuit (done at the sensor itself).
- Measure the resistance and voltage of the wires.
- Consult a service manual for the correct specifications (volts, ohms) for the vehicle.
- A common solution for this DTC is to replace the oxygen sensor Sensor #2 in bank 1.
More Information:
Video and Information on Oxygen Sensors (Example Link – Replace with relevant English video if possible)
