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9,253 diagnostic guides

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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.

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

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Severity

All severities9253 Low priority305 Check soon8256 Urgent621

Code family

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

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

Diagnostic codes

Showing 1033–1056 of 1223

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U3020Control Module Wake-up Circuit B HighCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3020 concerns control module wake-up circuit b high. Learn what this fault indicates and where to begin diagnosis.U3021Control Module Wake-up Circuit B PerformanceCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3021 concerns control module wake-up circuit b performance. Learn what this fault indicates and where to begin diagnosis.U3022Ignition Input Accessory/OffCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3022 concerns ignition input accessory/off. Learn what this fault indicates and where to begin diagnosis.U3023Control Module Input Power Circuit A - Ignition Input On/Start Circuit CorrelationCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3023 concerns control module input power circuit a - ignition input on/start circuit correlation. Learn what this fault indicates and where to begin diagnosis.U3024Control Module Input Power Circuit B - Ignition Input On/Start Circuit CorrelationCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3024 concerns control module input power circuit b - ignition input on/start circuit correlation. Learn what this fault indicates and where to begin diagnosis.U3025Control Module A Disable Circuit/OpenCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3025 concerns control module a disable circuit/open. Learn what this fault indicates and where to begin diagnosis.U3026Control Module A Disable Circuit LowCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3026 concerns control module a disable circuit low. Learn what this fault indicates and where to begin diagnosis.U3027Control Module A Disable Circuit HighCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3027 concerns control module a disable circuit high. Learn what this fault indicates and where to begin diagnosis.U3028Control Module A Disable Feedback CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3028 concerns control module a disable feedback circuit. Learn what this fault indicates and where to begin diagnosis.U3029Control Module A Disable Feedback Circuit LowCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3029 concerns control module a disable feedback circuit low. Learn what this fault indicates and where to begin diagnosis.U302AControl Module A Disable Feedback Circuit HighCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302A concerns control module a disable feedback circuit high. Learn what this fault indicates and where to begin diagnosis.U302BIgnition Output Accessory/On/StartCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302B concerns ignition output accessory/on/start. Learn what this fault indicates and where to begin diagnosis.U302CIgnition Output Off/On/StartCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302C concerns ignition output off/on/start. Learn what this fault indicates and where to begin diagnosis.U302DIgnition Output On/StartCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302D concerns ignition output on/start. Learn what this fault indicates and where to begin diagnosis.U302EIgnition Output OnCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302E concerns ignition output on. Learn what this fault indicates and where to begin diagnosis.U302FIgnition Output AccessoryCheck soonNetwork & Communication45–120 minutes for initial diagnosisU302F concerns ignition output accessory. Learn what this fault indicates and where to begin diagnosis.U3030Ignition Output StartCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3030 concerns ignition output start. Learn what this fault indicates and where to begin diagnosis.U3031Ignition Output OffCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3031 concerns ignition output off. Learn what this fault indicates and where to begin diagnosis.U3032Ignition Output Accessory/OffCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3032 concerns ignition output accessory/off. Learn what this fault indicates and where to begin diagnosis.U3033Control Module Security Certificate Missing/InvalidCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3033 concerns control module security certificate missing/invalid. Learn what this fault indicates and where to begin diagnosis.U3034Communication Authentication Key/Certificate Missing/InvalidCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3034 concerns communication authentication key/certificate missing/invalid. Learn what this fault indicates and where to begin diagnosis.U3035Communication Authentication Signal Invalid DataCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3035 concerns communication authentication signal invalid data. Learn what this fault indicates and where to begin diagnosis.U3036Communication Authentication Signal PerformanceCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3036 concerns communication authentication signal performance. Learn what this fault indicates and where to begin diagnosis.U3500Control Module Input Power A Circuit Range/PerformanceCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3500 concerns control module input power a circuit range/performance. Learn what this fault indicates and where to begin diagnosis.