GarageDex

OBD-II Trouble Codes

Your check-engine light stores a code. Look yours up for what it means, the common causes ranked by likelihood, the symptoms, how to fix it, and whether it's safe to keep driving. Definitions from the open SAE dataset; diagnostics reviewed by the GarageDex team.

Ignition & misfire

P0300 - Random/Multiple Cylinder Misfire DetectedP0301 - Cylinder 1 Misfire DetectedP0302 - Cylinder 2 Misfire DetectedP0303 - Cylinder 3 Misfire DetectedP0304 - Cylinder 4 Misfire Detected

Fuel & air metering

P0171 - System Too Lean (Bank 1)P0172 - System Too Rich (Bank 1)P0174 - System Too Lean (Bank 2)

Emissions & catalyst

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)P0430 - Catalyst System Efficiency Below Threshold (Bank 2)

Cooling system

P0128 - Coolant Temperature Below Thermostat Regulating TemperatureP0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

EVAP (fuel vapor)

P0455 - EVAP System Leak Detected (Large Leak)P0442 - EVAP System Leak Detected (Small Leak)P0446 - EVAP System Vent Control Circuit

Emissions & EGR

P0401 - EGR Flow Insufficient

Oxygen sensor

P0135 - O2 Sensor Heater Circuit (Bank 1, Sensor 1)P0141 - O2 Sensor Heater Circuit (Bank 1, Sensor 2)P0138 - O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)P0161 - O2 Sensor Heater Circuit (Bank 2, Sensor 2)

Sensors

P0113 - Intake Air Temperature Sensor Circuit HighP0101 - Mass Air Flow (MAF) Sensor Circuit Range/PerformanceP0121 - Throttle/Pedal Position Sensor A Circuit Range/PerformanceP0325 - Knock Sensor Circuit (Bank 1)P0340 - Camshaft Position Sensor A Circuit (Bank 1)P0344 - Camshaft Position Sensor A Circuit Intermittent (Bank 1)

Variable valve timing

P0011 - Camshaft Position - Timing Over-Advanced (Bank 1)P0016 - Crankshaft/Camshaft Position Correlation (Bank 1 Sensor A)

Idle & throttle

P0505 - Idle Air Control System

Charging system

P0562 - System Voltage LowP0563 - System Voltage High

Transmission

P0700 - Transmission Control System (MIL Request)