DIAGNOSTIC REFERENCE
A code is a starting point.
Look up an OBD-II fault code to understand the monitored condition, possible causes and a sensible diagnostic sequence.
Available fault codes
- P0101 · Mass or volume air flow circuit range/performanceFuel and air →
- P0171 · System too lean (Bank 1)Fuel and air →
- P0300 · Random or multiple cylinder misfire detectedCombustion →
- P0301 · Cylinder 1 misfire detectedCombustion →
- P0302 · Cylinder 2 misfire detectedCombustion →
- P0303 · Cylinder 3 misfire detectedCombustion →
- P0304 · Cylinder 4 misfire detectedCombustion →
- P0420 · Catalyst system efficiency below threshold (Bank 1)Emissions →
- P0442 · Evaporative emission system leak detected (small leak)Evaporative emissions →
- P0455 · Evaporative emission system leak detected (gross leak / no flow)Evaporative emissions →
A fault code identifies a detected condition, not a confirmed failed component. The manufacturer’s service procedure and vehicle-specific test results determine the repair.