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 root of the problem.  The engine light, turned on by the ECU 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 be causing 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 P0200 – P0209

• P0200 – Injector Circuit Malfunction
  • causes: Faulty injectors, wiring or connector, ECM.
• P0201 – Injector Circuit Malfunction – Cylinder 1
  • causes: Faulty injector in cylinder 1, wiring, ECM.
• P0202 – Injector Circuit Malfunction – Cylinder 2
  • causes: Same as P0201, but cylinder 2.
• P0203 – Injector Circuit Malfunction – Cylinder 3
  • causes: Same as P0201, but cylinder 3.
• P0204 – Injector Circuit Malfunction – Cylinder 4
  • causes: Same as P0201, but cylinder 4.
• P0205 – Injector Circuit Malfunction – Cylinder 5
  • causes: Same as P0201, but cylinder 5.
• P0206 – Injector Circuit Malfunction – Cylinder 6
  • causes: Same as P0201, but cylinder 6.
• P0207 – Injector Circuit Malfunction – Cylinder 7
  • causes: Same as P0201, but cylinder 7.
• P0208 – Injector Circuit Malfunction – Cylinder 8
  • causes: Same as P0201, but cylinder 8.
• P0209 – Injector Circuit Malfunction – Cylinder 9
  • causes: Same as P0201, but cylinder 9.

OBD / OBDII DTC P0210 – P0219

• P0210 – Injector Circuit Malfunction – Cylinder 10
  • causes: Same as P0201, but cylinder 10.
• P0211 – Injector Circuit Malfunction – Cylinder 11
  • causes: Same as P0201, but cylinder 11.
• P0212 – Injector Circuit Malfunction – Cylinder 12
  • causes: Same as P0201, but cylinder 12.
• P0213 – Cold Start Injector 1 Malfunction
  • causes: Faulty cold start injector, wiring or connector.
• P0214 – Cold Start Injector 2 Malfunction
  • causes: Same as P0213.
• P0215 – Engine Shutoff Solenoid Malfunction
  • causes: Faulty solenoid, wiring or connector, ECM.
• P0216 – Injection Timing Control Circuit Malfunction
  • causes: Wiring issues, faulty injection timing control, ECM.
• P0217 – Engine Overtemp Condition
  • causes: Cooling system failure, low coolant level, faulty thermostat.
• P0218 – Transmission Over Temperature Condition
  • causes: Low transmission fluid, faulty transmission cooler, transmission overuse.
• P0219 – Engine Overspeed Condition
  • causes: Mechanical failure, faulty sensors, ECM.

OBD / OBDII DTC P0220 – P0229

• P0220 – Throttle/Pedal Position Sensor/Switch ‘B’ Circuit Malfunction
  • causes: Faulty throttle position sensor, wiring or connector.
• P0221 – Throttle/Pedal Position Sensor/Switch ‘B’ Circuit Range/Performance Problem
  • causes: Faulty throttle position sensor, wiring, poor electrical connection.
• P0222 – Throttle/Pedal Position Sensor/Switch ‘B’ Circuit Low Input
  • causes: Short to ground, faulty sensor, wiring.
• P0223 – Throttle/Pedal Position Sensor/Switch ‘B’ Circuit High Input
  • causes: Short to power, faulty sensor, wiring.
• P0224 – Throttle/Pedal Position Sensor/Switch ‘B’ Circuit Intermittent
  • causes: Faulty sensor, loose or corroded connectors, wiring.
• P0225 – Throttle/Pedal Position Sensor/Switch ‘C’ Circuit Malfunction
  • causes: Faulty throttle position sensor, wiring or connector.
• P0226 – Throttle/Pedal Position Sensor/Switch ‘C’ Circuit Range/Performance Problem
  • causes: Faulty throttle position sensor, wiring, poor electrical connection.
• P0227 – Throttle/Pedal Position Sensor/Switch ‘C’ Circuit Low Input
  • causes: Short to ground, faulty sensor, wiring.
• P0228 – Throttle/Pedal Position Sensor/Switch ‘C’ Circuit High Input
  • causes: Short to power, faulty sensor, wiring.
• P0229 – Throttle/Pedal Position Sensor/Switch ‘C’ Circuit Intermittent
  • causes: Faulty sensor, loose or corroded connectors, wiring.

OBD / OBDII DTC P0230 – P0239

• P0230 – Fuel Pump Primary Circuit Malfunction
  • causes: Faulty fuel pump relay, wiring or connector, ECM.
• P0231 – Fuel Pump Secondary Circuit Low
  • causes: Faulty fuel pump, wiring or connector, fuse.
• P0232 – Fuel Pump Secondary Circuit High
  • causes: Short to power, wiring or connector, faulty fuel pump.
• P0233 – Fuel Pump Secondary Circuit Intermittent
  • causes: Loose or corroded connectors, wiring, intermittent fuel pump.
• P0234 – Engine Overboost Condition
  • causes: Faulty turbocharger/supercharger, wastegate, pressure sensor.
• P0235 – Turbocharger/Supercharger Boost Sensor ‘A’ Circuit Malfunction
  • causes: Faulty boost sensor, wiring or connector.
• P0236 – Turbocharger/Supercharger Boost Sensor ‘A’ Circuit Range/Performance
  • causes: Faulty sensor, turbocharger/supercharger, wiring.
• P0237 – Turbocharger/Supercharger Boost Sensor ‘A’ Circuit Low
  • causes: Short to ground, faulty sensor, wiring.
• P0238 – Turbocharger/Supercharger Boost Sensor ‘A’ Circuit High
  • causes: Short to power, faulty sensor, wiring.
• P0239 – Turbocharger/Supercharger Boost Sensor ‘B’ Circuit Malfunction
  • causes: Faulty boost sensor, wiring or connector.

OBD / OBDII DTC P0240 – P0249

• P0240 – Turbocharger/Supercharger Boost Sensor ‘B’ Circuit Range/Performance
  • causes: Faulty sensor, turbocharger/supercharger, wiring.
• P0241 – Turbocharger/Supercharger Boost Sensor ‘B’ Circuit Low
  • causes: Short to ground, faulty sensor, wiring.
• P0242 – Turbocharger/Supercharger Boost Sensor ‘B’ Circuit High
  • causes: Short to power, faulty sensor, wiring.
• P0243 – Turbocharger Wastegate Solenoid ‘A’ Malfunction
  • causes: Faulty wastegate solenoid, wiring or connector.
• P0244 – Turbocharger Wastegate Solenoid ‘A’ Range/Performance
  • causes: Faulty solenoid, turbocharger, wiring.
• P0245 – Turbocharger Wastegate Solenoid ‘A’ Low
  • causes: Short to ground, faulty solenoid, wiring.
• P0246 – Turbocharger Wastegate Solenoid ‘A’ High
  • causes: Short to power, faulty solenoid, wiring.
• P0247 – Turbocharger Wastegate Solenoid ‘B’ Malfunction
  • causes: Faulty wastegate solenoid, wiring or connector.
• P0248 – Turbocharger Wastegate Solenoid ‘B’ Range/Performance
  • causes: Faulty solenoid, turbocharger, wiring.
• P0249 – Turbocharger Wastegate Solenoid ‘B’ Low
  • causes: Short to ground, faulty solenoid, wiring.

OBD / OBDII DTC P0250 – P0259

• P0250 – Turbocharger Wastegate Solenoid ‘B’ High
  • causes: Short to power, faulty solenoid, wiring.
• P0251 – Injection Pump Fuel Metering Control ‘A’ Malfunction (Cam/Rotor/Injector)
  • causes: Faulty injection pump, cam/rotor/injector issues, or connector.
• P0252 – Injection Pump Fuel Metering Control ‘A’ Range/Performance (Cam/Rotor/Injector)
  • causes: Same as P0251.
• P0253 – Injection Pump Fuel Metering Control ‘A’ Low (Cam/Rotor/Injector)
  • causes: Short to ground, faulty injection pump, wiring.
• P0254 – Injection Pump Fuel Metering Control ‘A’ High (Cam/Rotor/Injector)
  • causes: Short to power, faulty injection pump, wiring.
• P0255 – Injection Pump Fuel Metering Control ‘A’ Intermittent (Cam/Rotor/Injector)
  • causes: Faulty injection pump, intermittent electrical connections, wiring.
• P0256 – Injection Pump Fuel Metering Control ‘B’ Malfunction (Cam/Rotor/Injector)
  • causes: Faulty injection pump, cam/rotor/injector, wiring or connector.
• P0257 – Injection Pump Fuel Metering Control ‘B’ Range/Performance (Cam/Rotor/Injector)
  • causes: Same as P0256.
• P0258 – Injection Pump Fuel Metering Control ‘B’ Low (Cam/Rotor/Injector)
  • causes: Short to ground, faulty injection pump, wiring.
• P0259 – Injection Pump Fuel Metering Control ‘B’ High (Cam/Rotor/Injector)
  • causes: Short to power, faulty injection pump, wiring.

OBD / OBDII DTC P0260 – P0269

• P0260 – Injection Pump Fuel Metering Control ‘B’ Intermittent (Cam/Rotor/Injector)
  • causes: Faulty injection pump, intermittent electrical connections, wiring.
• P0261 – Cylinder 1 Injector Circuit Low
  • causes: Short to ground, faulty injector, wiring.
• P0262 – Cylinder 1 Injector Circuit High
  • causes: Short to power, faulty injector, wiring.
• P0263 – Cylinder 1 Contribution/Balance Fault
  • causes: Faulty injector, engine mechanical, fuel system.
• P0264 – Cylinder 2 Injector Circuit Low
  • causes: Short to ground, faulty injector, wiring.
• P0265 – Cylinder 2 Injector Circuit High
  • causes: Short to power, faulty injector, wiring.
• P0266 – Cylinder 2 Contribution/Balance Fault
  • causes: Same as P0263.
• P0267 – Cylinder 3 Injector Circuit Low
  • causes: Same as P0261.
• P0268 – Cylinder 3 Injector Circuit High
  • causes: Same as P0262.
• P0269 – Cylinder 3 Contribution/Balance Fault
  • causes: Same as P0263.

OBD / OBDII DTC P0270 – P0279

• P0270 – Cylinder 4 Injector Circuit Low
  • causes: Same as P0261.
• P0271 – Cylinder 4 Injector Circuit High
  • causes: Same as P0262.
• P0272 – Cylinder 4 Contribution/Balance Fault
  • causes: Same as P0263.
• P0273 – Cylinder 5 Injector Circuit Low
  • causes: Same as P0261.
• P0274 – Cylinder 5 Injector Circuit High
  • causes: Same as P0262.
• P0275 – Cylinder 5 Contribution/Balance Fault
  • causes: Faulty injector, engine mechanical, fuel system.
• P0276 – Cylinder 6 Injector Circuit Low
  • causes: Short to ground, faulty injector, wiring.
• P0277 – Cylinder 6 Injector Circuit High
  • causes: Short to power, faulty injector, wiring.
• P0278 – Cylinder 6 Contribution/Balance Fault
  • causes: Same as P0275.
• P0279 – Cylinder 7 Injector Circuit Low
  • causes: Same as P0276.

OBD / OBDII DTC P0280 – P0289

• P0280 – Cylinder 7 Injector Circuit High
  • causes: Same as P0277.
• P0281 – Cylinder 7 Contribution/Balance Fault
  • causes: Same as P0275.
• P0282 – Cylinder 8 Injector Circuit Low
  • causes: Same as P0276.
• P0283 – Cylinder 8 Injector Circuit High
  • causes: Same as P0277.
• P0284 – Cylinder 8 Contribution/Balance Fault
  • causes: Same as P0275.
• P0285 – Cylinder 9 Injector Circuit Low
  • causes: Same as P0276.
• P0286 – Cylinder 9 Injector Circuit High
  • causes: Same as P0277.
• P0287 – Cylinder 9 Contribution/Balance Fault
  • causes: Same as P0275.
• P0288 – Cylinder 10 Injector Circuit Low
  • causes: Same as P0276.
• P0289 – Cylinder 10 Injector Circuit High
  • causes: Same as P0277.

OBD / OBDII DTC P0290 – P0299

• P0290 – Cylinder 10 Contribution/Balance Fault
  • causes: Same as P0275.
• P0291 – Cylinder 11 Injector Circuit Low
  • causes: Same as P0276.
• P0292 – Cylinder 11 Injector Circuit High
  • causes: Same as P0277.
• P0293 – Cylinder 11 Contribution/Balance Fault
  • causes: Same as P0275.
• P0294 – Cylinder 12 Injector Circuit Low
  • causes: Same as P0276.
• P0295 – Cylinder 12 Injector Circuit High
  • causes: Same as P0277.
• P0296 – Cylinder 12 Contribution/Balance Fault
  • causes: Same as P0275.
• P0297 – Vehicle Overspeed Condition
  • causes: Driver behavior, speedometer, ECM.
• P0298 – Engine Oil Over Temperature Condition
  • causes: Low oil level, faulty oil temperature sensor, cooling system.
• P0299 – Turbocharger/Supercharger ‘A’ Underboost Condition
  • causes: Turbocharger/supercharger fault, leak in the air intake system, wastegate or bypass valve, boost sensor.

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 ECU Codes Causing an Engine Light?

On-Board Diagnostic (OBD or OBDII ) codes are part of self-diagnostics.  The ECU and sensors work together to produce DTCs, illuminating the engine light.  The codes don’t 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), mandated the first OBD systems.  OBD, introduced in the 1980s, was the first of its kind.  The evolution of OBD resulted 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 starting 1996.  OBDII has 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 were much better, making it easier to diagnosis and repair.