Not all OBDII codes cause an engine light, OBD codes or DTC (diagnostic trouble code) are stored by the ECU (Engine Control Unit) or PCM (Powertrain Control Module) to point the mechanic to the cause.  The engine light is an indicator of problems.  The engine light on its own does not provide details, but reading the stored DTC is a good pointer to where the issue is.

If a DTC is stored in your ECU, it doesn’t necessary mean that there will be an engine light.  In fact no other indicator may be present.  The engine light is typically reserved for drivability or emission problems.  If you’re a DIY person, you should invest in a good OBDII scanner, now available with bluetooth.

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OBD / OBDII DTC stored in the ECU (May cause an engine light):

1. Powertrain Codes (P0XXX, P2XXX, P34XX – P39XX)
   • P0001 – P0099: Fuel and Air Metering
   • P0100 – P0199: Fuel and Air Metering
   • P0200 – P0299: Fuel and Air Metering (Injector Circuit)
   • P0300 – P0399: Ignition System or Misfire
   • P0400 – P0499: Auxiliary Emissions Controls
   • P0500 – P0599: Vehicle Speed Controls and Idle Control System
   • P0600 – P0699: Computer Output Circuit
   • P0700 – P0799: Transmission
   • P0800 – P0899: Transmission
   • P0900 – P0999: clutch and auxiliary emission control
   • P1XXX: Manufacturer-specific codes

Powertrain Codes

• P0001 – Fuel Volume Regulator Control Circuit/Open
  • causes: Faulty fuel volume regulator, wiring or connector issues.
• P0002 – Fuel Volume Regulator Control Circuit Range/Performance
  • causes: Faulty regulator, electrical connection issues.
• P0003 – Fuel Volume Regulator Control Circuit Low
  • causes: Short in wiring, faulty regulator.
• P0004 – Fuel Volume Regulator Control Circuit High
  • causes: Wiring short to power, faulty regulator.
• P0005 – Fuel Shutoff Valve ‘A’ Control Circuit/Open
  • causes: Faulty fuel shutoff valve, wiring or connector issues.
• P0006 – Fuel Shutoff Valve ‘A’ Control Circuit Low
  • causes: Short in wiring, faulty shutoff valve.
• P0007 – Fuel Shutoff Valve ‘A’ Control Circuit High
  • causes: Wiring short to power, faulty shutoff valve.
• P0008 – Engine Position System Performance Bank 1
  • Affecting performance.
  • causes: Stretched timing chain, worn gears, faulty sensors.  Usually relates to the timing chain or belt.
• P0009 – Engine Position System Performance Bank 2
  • causes: Same as P0008, but specific to bank 2.

OBD / OBDII DTC P0010-P0019

• P0010 – ‘A’ Camshaft Position Actuator Circuit (Bank 1)
  • causes: Faulty camshaft position actuator, wiring issues.
• P0011 – ‘A’ Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)
  • Camshaft timing for bank 1 is too advanced or the system’s performance is off.
  • causes: Oil flow issues, timing issues, faulty camshaft position sensor.
• P0012 – ‘A’ Camshaft Position – Timing Over-Retarded (Bank 1)
  • causes: Same as P0011 but with timing being retarded.
• P0013 – ‘B’ Camshaft Position Actuator Circuit (Bank 1)
  • causes: Faulty camshaft position actuator, electrical issues.
• P0014 – ‘B’ Camshaft Position – Timing Over-Advanced or System Performance (Bank 1)
  • ‘B’ Camshaft position for bank 1 is too advanced or system performance is off.
  • causes: Oil flow problems, timing issues, faulty sensors.
• P0015 – ‘B’ Camshaft Position – Timing Over-Retarded (Bank 1)
  • causes: Similar to P0014 but with timing being retarded.
• P0016 – Crankshaft Position – Camshaft Position Correlation (Bank 1 Sensor A)
  • Misalignment between the crankshaft and camshaft positions in bank 1.
  • causes: Timing belt/chain issues, faulty sensors, mechanical engine problems.
• P0017 – Crankshaft Position – Camshaft Position Correlation (Bank 1 Sensor B)
  • Common causes: Same as P0016, but for sensor B in bank 1.
• P0018 – Crankshaft Position – Camshaft Position Correlation (Bank 2 Sensor A)
  • Misalignment between the crankshaft and camshaft positions in bank 2.
  • causes: Similar to P0016, but specific to bank 2.
• P0019 – Crankshaft Position – Camshaft Position Correlation (Bank 2 Sensor B)
  • causes: Same as P0018, but for sensor B in bank 2.

OBD / OBDII DTC P0020-P0029

• P0020 – ‘A’ Camshaft Position Actuator Circuit (Bank 2)
  • causes: Faulty camshaft position actuator, electrical issues.
• P0021 – ‘A’ Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)
  • Camshaft timing for bank 2 is too advanced or the system’s performance is off.
  • causes: Oil flow issues, timing issues, faulty camshaft position sensor.
• P0022 – ‘A’ Camshaft Position – Timing Over-Retarded (Bank 2)
  • causes: Same as P0021, but with timing being retarded.
• P0023 – ‘B’ Camshaft Position Actuator Circuit (Bank 2)
  • causes: Faulty camshaft position actuator, electrical issues.
• P0024 – ‘B’ Camshaft Position – Timing Over-Advanced or System Performance (Bank 2)
  • ‘B’ Camshaft position for bank 2 is too advanced or system performance is off.
  • causes: Oil flow problems, timing issues, faulty sensors.
• P0025 – ‘B’ Camshaft Position – Timing Over-Retarded (Bank 2)
  • causes: Similar to P0024, but with timing being retarded.
• P0026 – Intake Valve Control Solenoid Circuit Range/Performance (Bank 1)
  • Problem with the performance or range of the intake valve control solenoid in bank 1.
  • causes: Faulty solenoid, wiring issues, mechanical faults in valve operation.
• P0027 – Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 1)
  • causes: Same as P0026, but for the exhaust valve control solenoid in bank 1.
• P0028 – Intake Valve Control Solenoid Circuit Range/Performance (Bank 2)
  • causes: Same as P0026, but specific to bank 2.
• P0029 – Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 2)
  • causes: Same as P0028, but for the exhaust valve control solenoid in bank 2.

OBD / OBDII DTC P0030-P0039

• P0030 – HO2S Heater Control Circuit (Bank 1 Sensor 1)
  • causes: Faulty sensor, wiring issues, control circuit problems.
• P0031 – HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
  • causes: Wiring short to ground, faulty sensor.
• P0032 – HO2S Heater Control Circuit High (Bank 1 Sensor 1)
  • causes: Wiring short to power, faulty sensor.
• P0033 – Turbocharger/Supercharger Bypass Valve Control Circuit
  • Issue: Problem with the control circuit of the turbocharger or supercharger bypass valve.
  • causes: Faulty bypass valve, wiring issues, solenoid failure.
• P0034 – Turbocharger/Supercharger Bypass Valve Control Circuit Low
  • causes: Short to ground in wiring, faulty bypass valve solenoid.
• P0035 – Turbocharger/Supercharger Bypass Valve Control Circuit High
  • causes: Short to power in wiring, faulty bypass valve solenoid.
• P0036 – HO2S Heater Control Circuit (Bank 1 Sensor 2)
  • causes: Faulty sensor, wiring issues, control circuit problems.
• P0037 – HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
  • causes: Wiring short to ground, faulty sensor.
• P0038 – HO2S Heater Control Circuit High (Bank 1 Sensor 2)
  • causes: Wiring short to power, faulty sensor.
• P0039 – Turbocharger/Supercharger Bypass Valve Control Circuit Range/Performance
  • causes: Faulty bypass valve, wiring or solenoid issues, turbocharger or supercharger faults.

OBD / OBDII DTC P0040-P0049

• P0040 – Upstream Oxygen Sensors Swapped From Bank To Bank
  • The upstream oxygen sensors are swapped between bank 1 and bank 2.
  • causes: Incorrect sensor installation, wiring issues.
• P0041 – Downstream Oxygen Sensors Swapped From Bank To Bank
  • The downstream oxygen sensors are swapped between bank 1 and bank 2.
  • causes: Incorrect sensor installation, wiring issues.
• P0042 – HO2S Heater Control Circuit (Bank 1 Sensor 3)
  • causes: Faulty sensor, wiring issues.
• P0043 – HO2S Heater Control Circuit Low (Bank 1 Sensor 3)
  • causes: Wiring short to ground, faulty HO2S heater.
• P0044 – HO2S Heater Control Circuit High (Bank 1 Sensor 3)
  • causes: Wiring short to power, faulty HO2S heater.
• P0045 – Turbo/Super Charger Boost Control Solenoid Circuit/Open
  • causes: Faulty boost control solenoid, wiring or connector issues.
• P0046 – Turbo/Super Charger Boost Control Solenoid Circuit Range/Performance
  • causes: Faulty solenoid, wiring problems, turbocharger or supercharger issues.
• P0047 – Turbo/Super Charger Boost Control Solenoid Circuit Low
  • causes: Short to ground in wiring, faulty solenoid.
• P0048 – Turbo/Super Charger Boost Control Solenoid Circuit High
  • causes: Short to power in wiring, faulty solenoid.
• P0049 – Turbo/Super Charger Turbine Overspeed
  • The turbocharger or supercharger turbine is spinning too fast (overspeed condition).
  • causes: Turbocharger or supercharger malfunction, control system issues.

OBD / OBDII DTC P0050-P0059

• P0050 – HO2S Heater Control Circuit (Bank 2 Sensor 1)
  • causes: Faulty sensor, wiring or connector issues.
• P0051 – HO2S Heater Control Circuit Low (Bank 2 Sensor 1)
  • causes: Short to ground in wiring, faulty sensor.
• P0052 – HO2S Heater Control Circuit High (Bank 2 Sensor 1)
  • causes: Short to power in wiring, faulty sensor.
• P0053 – HO2S Heater Resistance (Bank 1 Sensor 1)
  • causes: Faulty sensor, wiring or connector issues.
• P0054 – HO2S Heater Resistance (Bank 1 Sensor 2)
  • causes: Same as P0053, but for bank 1, sensor 2.
• P0055 – HO2S Heater Resistance (Bank 1 Sensor 3)
  • causes: Same as P0053, but for bank 1, sensor 3.
• P0056 – HO2S Heater Control Circuit (Bank 2 Sensor 2)
  • causes: Faulty sensor, wiring issues.
• P0057 – HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
  • causes: Short to ground in wiring, faulty sensor.
• P0058 – HO2S Heater Control Circuit High (Bank 2 Sensor 2)
  • causes: Short to power in wiring, faulty sensor.
• P0059 – HO2S Heater Resistance (Bank 2 Sensor 1)
  • causes: Faulty sensor, wiring issues.

OBD / OBDII DTC P0060-P0069

• P0060 – HO2S Heater Resistance (Bank 2 Sensor 2)
  • Resistance problem in the heater element of the oxygen sensor in bank 2, sensor 2.
  • causes: Faulty sensor, wiring or connector issues.
• P0061 – HO2S Heater Resistance (Bank 2 Sensor 3)
  • Resistance problem in the heater element of the oxygen sensor in bank 2, sensor 3.
  • causes: Faulty sensor, wiring issues.
• P0062 – HO2S Heater Control Circuit (Bank 2 Sensor 3)
  • Problem with the heater control circuit of the oxygen sensor in bank 2, sensor 3.
  • causes: Faulty sensor, wiring issues.
• P0063 – HO2S Heater Control Circuit Low (Bank 2 Sensor 3)
  • causes: Short to ground in wiring, faulty sensor.
• P0064 – HO2S Heater Control Circuit High (Bank 2 Sensor 3)
  • causes: Short to power in wiring, faulty sensor.
• P0065 – Air Assisted Injector Control Range/Performance
  • causes: Faulty air-assisted injector system, sensor issues, wiring or connector problems.
• P0066 – Air Assisted Injector Control Circuit or Circuit Low
  • causes: Wiring short to ground, faulty air-assisted injector system.
• P0067 – Air Assisted Injector Control Circuit High
  • causes: Wiring short to power, faulty air-assisted injector system.
• P0068 – Manifold Absolute Pressure/Mass Air Flow – Throttle Position Correlation
  • Discrepancy between the manifold absolute pressure/mass air flow readings and the throttle position.
  • causes: Faulty sensors, vacuum leaks, throttle issues.
• P0069 – Manifold Absolute Pressure – Barometric Pressure Correlation
  • Discrepancy between the manifold absolute pressure and barometric pressure readings.
  • causes: Faulty MAP sensor, issues with the barometric sensor, environmental factors.

OBD / OBDII DTC P0070-P0079

• P0070 – Ambient Air Temperature Sensor Circuit
  • causes: Faulty ambient air temperature sensor, wiring or connector issues.
• P0071 – Ambient Air Temperature Sensor Range/Performance
  • causes: Faulty sensor, environmental factors affecting sensor performance.
• P0072 – Ambient Air Temperature Sensor Circuit Low Input
  • causes: Short to ground in wiring, faulty sensor.
• P0073 – Ambient Air Temperature Sensor Circuit High Input
  • causes: Short to power in wiring, faulty sensor.
• P0074 – Ambient Air Temperature Sensor Circuit Intermittent
  • causes: Loose connections, faulty sensor, wiring issues.
• P0075 – Intake Valve Control Solenoid Circuit (Bank 1)
  • causes: Faulty solenoid, wiring or connector issues.
• P0076 – Intake Valve Control Solenoid Circuit Low (Bank 1)
  • causes: Short to ground in wiring, faulty solenoid.
• P0077 – Intake Valve Control Solenoid Circuit High (Bank 1)
  • causes: Short to power in wiring, faulty solenoid.
• P0078 – Exhaust Valve Control Solenoid Circuit (Bank 1)
  • causes: Faulty solenoid, wiring or connector issues.
• P0079 – Exhaust Valve Control Solenoid Circuit Low (Bank 1)
  • causes: Short to ground in wiring, faulty solenoid.

OBD / OBDII DTC P0080-P0089

• P0080 – Exhaust Valve Control Solenoid Circuit High (Bank 1)
  • causes: Short to power in wiring, faulty solenoid.
• P0081 – Intake Valve Control Solenoid Circuit (Bank 2)
  • causes: Faulty solenoid, wiring or connector issues.
• P0082 – Intake Valve Control Solenoid Circuit Low (Bank 2)
  • causes: Short to ground in wiring, faulty solenoid.
• P0083 – Intake Valve Control Solenoid Circuit High (Bank 2)
  • causes: Short to power in wiring, faulty solenoid.
• P0084 – Exhaust Valve Control Solenoid Circuit (Bank 2)
  • causes: Faulty solenoid, wiring or connector issues.
• P0085 – Exhaust Valve Control Solenoid Circuit Low (Bank 2)
  • causes: Short to ground in wiring, faulty solenoid.
• P0086 – Exhaust Valve Control Solenoid Circuit High (Bank 2)
  • causes: Short to power in wiring, faulty solenoid.
• P0087 – Fuel Rail/System Pressure – Too Low
  • causes: Faulty fuel pump, clogged fuel filter, fuel pressure regulator issues.
• P0088 – Fuel Rail/System Pressure – Too High
  • causes: Faulty fuel pressure regulator, clogged return line, pump issues.
• P0089 – Fuel Pressure Regulator 1 Performance
  • causes: Faulty regulator, sensor issues, wiring problems.

OBD / OBDII DTC P0090-P0099

• P0090 – Fuel Pressure Regulator 1 Control Circuit/Open
  • causes: Faulty regulator, wiring or connector issues.
• P0091 – Fuel Pressure Regulator 1 Control Circuit Low
  • causes: Short to ground in wiring, faulty regulator.
• P0092 – Fuel Pressure Regulator 1 Control Circuit High
  • causes: Short to power in wiring, faulty regulator.
• P0093 – Fuel System Leak Detected – Large Leak
  • causes: Leaking fuel lines or connectors, faulty fuel tank.
• P0094 – Fuel System Leak Detected – Small Leak
  • causes: Small leaks in fuel lines, connectors, injectors.
• P0095 – Intake Air Temperature Sensor 2 Circuit
  • causes: Faulty sensor, wiring or connector issues.
• P0096 – Intake Air Temperature Sensor 2 Circuit Range/Performance
  • causes: Faulty sensor, wiring problems, intake air temperature issues.
• P0097 – Intake Air Temperature Sensor 2 Circuit Low Input
  • causes: Short to ground in wiring, faulty intake air temperature sensor.
• P0098 – Intake Air Temperature Sensor 2 Circuit High Input
  • causes: Short to power in wiring, faulty intake air temperature sensor.
• P0099 – Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic
  • causes: Loose or corroded connectors, faulty sensor, wiring issues.

Why is my Engine Light on?

On-Board Diagnostic (OBD / OBDII) codes are stored within the Engine Control Unit (ECU) or Powertrain Control Module (PCM). These modules store the codes, monitor and control engine performance and emissions. When the system detects a fault or irregularity, it generates a diagnostic trouble code (DTC), which is stored in the ECU/PCM’s memory. This code can be retrieved using an OBD scanner, providing insights into issues.

Are These Codes Causing an Engine Light?

On-Board Diagnostic (OBD or OBDII ) codes are part of a vehicle’s self-diagnostic system.  The ECU and sensors work together to produce DTCs, sometimes resulting in an engine light.  The codes generated do not always cause an engine light.  The development of OBD systems began in the 1980s, driven by increasing environmental concerns and regulations, especially in California. The California Air Resources Board (CARB) played a key role in this, mandating the first OBD systems.  OBD, introduced in the 1980s, was the first system of its kind.  The evolution of OBD technology culminated in the universal OBDII standard in the mid-1990s.  It provided basic capabilities to monitor and diagnose vehicle functions, primarily for emissions control.  OBDII, introduced in the mid-1990s, is a more advanced and standardized system.  This OBDII advanced system was mandatory for all cars sold in the United States from 1996 onwards.  OBDII offers broader diagnostics, real-time data, and standardization across most vehicles.  This made it easier to diagnose and address issues.  OBDII’s standardized diagnostic trouble codes (DTC) and connector types are much better than the earlier OBD system, making it easier to diagnosis and repair.