Check Engine Light On: OBD2 Diagnosis Path
MIL illuminated with or without immediate drivability issues. Start with the related code pages below, then use scanner and guide pages to narrow down root cause and reduce unnecessary parts swaps.
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Code reader for a check engine light — see what the tool has to be able to do before you buy one.
Code reader for a check engine lightMost Related OBD2 Codes
P0171 · System Too Lean (Bank 1) P0300 · Random / Multiple Cylinder Misfire P0420 · Catalyst System Efficiency Below Threshold (Bank 1) P0442 · Evaporative Emission System Leak Detected (Small Leak) P0401 · Exhaust Gas Recirculation Flow Insufficient Detected B0020 · Front Passenger Side Airbag Deployment Control C0035 · Left Front Wheel Speed Sensor Circuit U0100 · Lost Communication With ECM/PCM
Related Scanner Intent Pages
Related Buying Guides
Tip: if your exact code is still unknown, start at OBDHacks scanner input and then return to this symptom cluster for deeper troubleshooting.