OBD-II code library
Check-engine codes, explained honestly
What each code means, whether it's safe to keep driving, what the live sensor data shows, and what actually fixes it — cheapest first. In-depth guides for the codes people actually search.
P0420
Catalyst System Efficiency Below Threshold (Bank 1)
Drive normally — check soon
P0300
Random/Multiple Cylinder Misfire Detected
Caution
P0171
Fuel Trim System Lean (Bank 1)
Get it checked soon
P0174
Fuel Trim too Lean (Bank 2)
Get it checked soon
P0128
Coolant Thermostat Malfunction
Drive normally — check soon
P0442
Evaporative Emission Control System Leak Detected (small leak)
Drive normally — check soon
P0455
Evaporative Emission Control System Leak Detected (gross leak)
Drive normally — check soon
P0401
Exhaust Gas Recirculation Flow Insufficient Detected
Get it checked soon
P0011
“A” Camshaft Position — Timing Over-Advanced (Bank 1)
Get it checked soon
P0016
Crankshaft Position — Camshaft Position Correlation (Bank 1 Sensor A)
Caution
P0102
Mass or Volume Air Flow Circuit Low Input
Get it checked soon
P0113
Intake Air Temperature Circuit High Input
Drive normally — check soon
P0131
O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
Get it checked soon
P0301
Cylinder 1 Misfire Detected
Caution
P0303
Cylinder 3 Misfire Detected
Caution
P0325
Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
Get it checked soon
P0430
Catalyst System Efficiency Below Threshold (Bank 2)
Drive normally — check soon
P0700
Transmission Control System Malfunction
Get it checked soon
P0715
Input/Turbine Speed Sensor Circuit Malfunction
Get it checked soon
U0100
Lost Communication With ECM/PCM “A”
Caution
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