Find the cause of your fault code

Cars & SUVs, heavy trucks (J1939 SPN/FMI), or diesel & RVs — pick your vehicle type, then diagnose.

Free VIN decoder

Decode your VIN with the official NHTSA database, then we select the matching vehicle type for your code search.

Every code sheet uses one of these three levels. They are practical driving guidance — not a legal ruling.

OK to driveYou can usually keep driving for short trips, but schedule a diagnosis soon.
Check soonHave the vehicle checked soon; avoid long trips if symptoms worsen.
Stop the vehicleStop driving when safe and have the vehicle inspected before continuing.

Start from the mechanical system, then open the matching fault-code sheets.

Narrative primers on scanners, code letters, and heavy-truck J1939 — separate from individual code sheets.

Every code in our database — linked by vehicle type for easy navigation.

Diesel OBD codes that also apply to some light trucks and cars are listed under Diesel & RV (badge: also cars) — not duplicated under Cars & SUVs.