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Check engine light codes explained

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Fuel and air

P0087Fuel rail pressure too low P0171System too lean (Bank 1)P0172System too rich (Bank 1)P0174System too lean (Bank 2)P0175System too rich (Bank 2)P0299Turbocharger underboost P0505Idle control system malfunction P0506Idle speed lower than expected P0507Idle speed higher than expected P2187System too lean at idle (Bank 1)P2188System too rich at idle (Bank 1)P2279Intake air system leak

Ignition and misfires

P0300Random or multiple cylinder misfire P0301Cylinder 1 misfire detected P0302Cylinder 2 misfire detected P0303Cylinder 3 misfire detected P0304Cylinder 4 misfire detected P0305Cylinder 5 misfire detected P0306Cylinder 6 misfire detected P0307Cylinder 7 misfire detected P0308Cylinder 8 misfire detected

Emissions

P0401Exhaust gas recirculation (EGR) flow insufficient P0402Exhaust gas recirculation (EGR) flow excessive P0403Exhaust gas recirculation (EGR) control circuit P0420Catalyst system efficiency below threshold (Bank 1)P0430Catalyst system efficiency below threshold (Bank 2)P0440Evaporative emission (EVAP) system malfunction P0441Evaporative system incorrect purge flow P0442Evaporative system small leak detected P0443Evaporative purge control valve circuit P0446Evaporative vent control circuit P0455Evaporative system large leak detected P0456Evaporative system very small leak detected P0457Evaporative system leak (fuel cap loose or off)P2002Diesel particulate filter efficiency below threshold (Bank 1)

Engine sensors

P0101Mass air flow sensor range or performance P0102Mass air flow sensor circuit low input P0103Mass air flow sensor circuit high input P0106Manifold pressure (MAP) sensor range or performance P0107Manifold pressure (MAP) sensor circuit low input P0108Manifold pressure (MAP) sensor circuit high input P0111Intake air temperature sensor range or performance P0112Intake air temperature sensor circuit low input P0113Intake air temperature sensor circuit high input P0116Coolant temperature sensor range or performance P0117Coolant temperature sensor circuit low input P0118Coolant temperature sensor circuit high input P0121Throttle position sensor range or performance P0122Throttle position sensor circuit low input P0123Throttle position sensor circuit high input P0131Oxygen sensor circuit low voltage (Bank 1 Sensor 1)P0133Oxygen sensor slow response (Bank 1 Sensor 1)P0134Oxygen sensor no activity detected (Bank 1 Sensor 1)P0135Oxygen sensor heater circuit (Bank 1 Sensor 1)P0137Oxygen sensor circuit low voltage (Bank 1 Sensor 2)P0138Oxygen sensor circuit high voltage (Bank 1 Sensor 2)P0141Oxygen sensor heater circuit (Bank 1 Sensor 2)P0325Knock sensor circuit (Bank 1)P0335Crankshaft position sensor circuit P0340Camshaft position sensor circuit (Bank 1)P0341Camshaft position sensor range or performance (Bank 1)P0460Fuel level sensor circuit P2138Throttle or pedal position sensor voltage correlation

Timing and valves

P0010Intake camshaft actuator circuit (Bank 1)P0011Intake camshaft timing over-advanced (Bank 1)P0016Crankshaft and camshaft position do not match (Bank 1)

Cooling

P0128Coolant temperature below thermostat regulating temperature P0217Engine overtemperature condition P0480Cooling fan 1 control circuit

Transmission and speed

P0500Vehicle speed sensor malfunction P0700Transmission control system malfunction P0715Input or turbine speed sensor circuit P0720Output speed sensor circuit P0730Incorrect gear ratio P0741Torque converter clutch circuit performance or stuck off P0750Shift solenoid A malfunction

Electrical

P0562System voltage low P0563System voltage high

Network and modules

U0100Lost communication with engine computer (ECM/PCM)U0101Lost communication with transmission computer (TCM)U0121Lost communication with ABS control module U0140Lost communication with body control module

General information, not a diagnosis. Causes vary by make, model and engine. If you are unsure, have the car inspected.