Diagnostic library

Find an OBD2 code

Search the code from your scanner, then narrow the library by system, severity, or code family.

9,253 diagnostic guides

Sort

Find codes by symptomChoose what you notice to search matching code guides.

Rough idle or shakingVibration while stopped Hard to startLong cranking or no-start Engine stallsCuts out at idle or on the road Hesitates or loses powerSlow response when accelerating Battery light is onCharging system warning Harsh gear changesDelayed or rough shifting

A symptom can have several causes. Treat matching codes as clues and follow the diagnostic checks in each guide.

Urgent U · Network Clear all

Quick browse

Choose a vehicle system

Engine1049 Emissions515 Fuel1016 Sensors & Electronics2110 Transmission866 Electrical & Charging1797 Body & Restraints193 Chassis & Brakes479 Network & Communication1228

FiltersSeverity · family

Severity

All severities9253 Low priority305 Check soon8256 Urgent621

Code family

All families9253 P · Powertrain7353 B · Body193 C · Chassis479 U · Network1228

Vehicle coverage

These are generic OBD2 definitions. Exact make, model, engine, and year compatibility will appear after vehicle-fitment data is added.

Diagnostic codes

Showing 1–5 of 5

Most searched first

U0100Lost Communication With ECM/PCM AUrgentNetwork & Communication1–3 hours for initial diagnosisU0100 means Lost Communication With ECM/PCM A. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.U0101Lost Communication With Transmission Control ModuleUrgentNetwork & Communication1–3 hours for initial diagnosisU0101 means Lost Communication With Transmission Control Module. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.U0121Lost Communication With Anti-Lock Brake System Control ModuleUrgentNetwork & Communication1–3 hours for initial diagnosisU0121 means Lost Communication With Anti-Lock Brake System Control Module. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.U0131Lost Communication With Power Steering Control ModuleUrgentNetwork & Communication1–3 hours for initial diagnosisU0131 means Lost Communication With Power Steering Control Module. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.U0129Lost Communication With Brake System Control ModuleUrgentNetwork & Communication1–3 hours for initial diagnosisU0129 means Lost Communication With Brake System Control Module. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.