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.

Check soon P · Powertrain 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 817–840 of 6682

Most searched first

P040AEGR Temperature Sensor A CircuitCheck soonEmissions System30–120 minutes for initial diagnosisP040A relates to egr temperature sensor a circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P040BEGR Temperature Sensor A Circuit Range/PerformanceCheck soonEmissions System30–120 minutes for initial diagnosisP040B relates to egr temperature sensor a circuit range/performance. Check the fault conditions and vehicle-specific procedure before replacing parts.P040CEGR Temperature Sensor A Circuit LowCheck soonEmissions System30–120 minutes for initial diagnosisP040C relates to egr temperature sensor a circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P040DEGR Temperature Sensor A Circuit HighCheck soonEmissions System30–120 minutes for initial diagnosisP040D relates to egr temperature sensor a circuit high. Check the fault conditions and vehicle-specific procedure before replacing parts.P040EEGR Temperature Sensor A Circuit Intermittent/ErraticCheck soonEmissions System30–120 minutes for initial diagnosisP040E relates to egr temperature sensor a circuit intermittent/erratic. Check the fault conditions and vehicle-specific procedure before replacing parts.P040FEGR Temperature Sensor A/B CorrelationCheck soonEmissions System30–120 minutes for initial diagnosisP040F relates to egr temperature sensor a/b correlation. Check the fault conditions and vehicle-specific procedure before replacing parts.P0415AIR System Switching Valve B CircuitCheck soonSensors & Electronics30–120 minutes for initial diagnosisP0415 relates to air system switching valve b circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P0416AIR System Switching Valve B Circuit OpenCheck soonSensors & Electronics30–120 minutes for initial diagnosisP0416 relates to air system switching valve b circuit open. Check the fault conditions and vehicle-specific procedure before replacing parts.P0417AIR System Switching Valve B Circuit ShortedCheck soonSensors & Electronics30–120 minutes for initial diagnosisP0417 relates to air system switching valve b circuit shorted. Check the fault conditions and vehicle-specific procedure before replacing parts.P0418AIR System Control A CircuitCheck soonSensors & Electronics30–120 minutes for initial diagnosisP0418 relates to air system control a circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P0419AIR System Control B CircuitCheck soonSensors & Electronics30–120 minutes for initial diagnosisP0419 relates to air system control b circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P041AEGR Temperature Sensor B CircuitCheck soonEmissions System30–120 minutes for initial diagnosisP041A relates to egr temperature sensor b circuit. Check the fault conditions and vehicle-specific procedure before replacing parts.P041BEGR Temperature Sensor B Circuit Range/PerformanceCheck soonEmissions System30–120 minutes for initial diagnosisP041B relates to egr temperature sensor b circuit range/performance. Check the fault conditions and vehicle-specific procedure before replacing parts.P041CEGR Temperature Sensor B Circuit LowCheck soonEmissions System30–120 minutes for initial diagnosisP041C relates to egr temperature sensor b circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P041DEGR Temperature Sensor B Circuit HighCheck soonEmissions System30–120 minutes for initial diagnosisP041D relates to egr temperature sensor b circuit high. Check the fault conditions and vehicle-specific procedure before replacing parts.P041EEGR Temperature Sensor B Circuit Intermittent/ErraticCheck soonEmissions System30–120 minutes for initial diagnosisP041E relates to egr temperature sensor b circuit intermittent/erratic. Check the fault conditions and vehicle-specific procedure before replacing parts.P041FAIR System Switching Valve A Circuit LowCheck soonSensors & Electronics30–120 minutes for initial diagnosisP041F relates to air system switching valve a circuit low. Check the fault conditions and vehicle-specific procedure before replacing parts.P0424Heated Catalyst Temperature Below Threshold (Bank 1)Check soonEmissions System30–90 minutes for initial diagnosisP0424 indicates the monitored heated-catalyst temperature on Bank 1 is below the expected threshold. Learn what to inspect before replacing parts.P0425Catalyst Temperature Sensor Circuit (Bank 1, Sensor 1)Check soonEmissions System30–90 minutes for initial diagnosisP0425 indicates the control module detected a fault in the Bank 1 Sensor 1 catalyst-temperature-sensor circuit. Learn what to inspect before replacing parts.P0426Catalyst Temperature Sensor Circuit Range/Performance (Bank 1, Sensor 1)Check soonEmissions System30–90 minutes for initial diagnosisP0426 indicates the Bank 1 Sensor 1 catalyst-temperature signal is outside its expected range or does not respond plausibly. Learn what to inspect before replacing parts.P0427Catalyst Temperature Sensor Circuit Low (Bank 1, Sensor 1)Check soonEmissions System30–90 minutes for initial diagnosisP0427 indicates the Bank 1 Sensor 1 catalyst-temperature sensor circuit signal is below the expected electrical range. Learn what to inspect before replacing parts.P0428Catalyst Temperature Sensor Circuit High (Bank 1, Sensor 1)Check soonEmissions System30–90 minutes for initial diagnosisP0428 indicates the Bank 1 Sensor 1 catalyst-temperature sensor circuit signal is above the expected electrical range. Learn what to inspect before replacing parts.P0429Catalyst Heater Control Circuit (Bank 1)Check soonEmissions System30–90 minutes for initial diagnosisP0429 indicates the control module detected a fault in the Bank 1 catalyst-heater control circuit. Learn what to inspect before replacing parts.P042ACatalyst Temperature Sensor Circuit Bank 1 Sensor 2Check soonEmissions System30–120 minutes for initial diagnosisP042A relates to catalyst temperature sensor circuit bank 1 sensor 2. Check the fault conditions and vehicle-specific procedure before replacing parts.