Check Engine Light on
🔍 Diagnostic Note: Check Engine Light on can be caused by multiple issues. The codes below are the most common OBD2 diagnostic trouble codes associated with this symptom. Use the diagnostic steps on each code page to narrow down the root cause.
18 related OBD2 codes:
P0420 — Catalytic Converter System Efficiency Below Threshold (Bank 1)$400-$2500P0171 — System Too Lean (Bank 1)$100-$800P0455 — Evaporative Emission System Leak Detected (Gross Leak)$50-$600P0101 — Mass Air Flow (MAF) Sensor Circuit Range/Performance$80-$400P0135 — O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)$100-$350P0401 — Exhaust Gas Recirculation (EGR) Flow Insufficient$50-$500P0442 — Evaporative Emission System Small Leak Detected$50-$500P0500 — Vehicle Speed Sensor (VSS) Malfunction$100-$400U0100 — Lost Communication with ECM/PCM$200-$1500P0128 — Coolant Thermostat Below Regulating Temperature$80-$350P0138 — O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)$100-$350P0340 — Camshaft Position Sensor Circuit Malfunction$100-$600P0440 — Evaporative Emission Control System Malfunction$50-$500P0606 — ECM/PCM Processor Fault$500-$2000P0700 — Transmission Control System Malfunction$50-$3000P2101 — Throttle Actuator Control Motor Circuit Range/Performance$100-$800P0446 — EVAP Vent Control Circuit Malfunction$100-$400P0496 — EVAP System High Purge Flow$80-$350