Auto OBD-II Fault Code Diagnostics
Look up any OBD-II P-code — symptoms, root causes, DVOM tests, and step-by-step repair procedures. AI-guided diagnosis for cars, trucks, and SUVs.
Browse by System
Select a system category to see all related fault codes and diagnostic guidance.
Engine Performance
10 codesGeneral engine performance codes including power loss, rough running, and sensor faults.
Fuel Trim
36 codesShort and long-term fuel trim codes indicating rich or lean conditions.
Ignition & Misfire
16 codesSpark plug, ignition coil, and cylinder misfire fault codes.
EVAP System
9 codesEvaporative emission control system leak and valve fault codes.
O2 Sensor / AFR
6 codesOxygen sensor and air-fuel ratio sensor circuit and performance codes.
Catalyst Efficiency
Catalytic converter efficiency and performance fault codes.
Throttle & Airflow
3 codesThrottle body, MAF sensor, and intake airflow fault codes.
Transmission Codes
14 codesAutomatic and manual transmission shift, solenoid, and pressure codes.
ABS & Stability
20 codesAnti-lock brake system and electronic stability control fault codes.
Body & Comfort Systems
1 codesBody control module, HVAC, and comfort system fault codes.
Cooling System
5 codesEngine coolant temperature, thermostat, and cooling fan fault codes.
Charging System
Alternator, battery, and charging circuit fault codes.
Starting System
Starter motor, crankshaft position, and no-start fault codes.
Also diagnosing heavy-duty diesel?
AI Diesel Tech handles both OBD-II P-codes and J1939 SPN/FMI codes in the same platform. Switch between auto and diesel fault libraries instantly.
Get AI-Guided OBD-II Diagnosis
Enter any P-code and get step-by-step DVOM tests, component locations, and repair procedures — on your phone, at the vehicle.