Diagnostic library

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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.

Check soon U · Network Clear all

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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 1153–1176 of 1223

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U3561Cathode Bypass Valve Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3561 concerns cathode bypass valve control circuit. Learn what this fault indicates and where to begin diagnosis.U3562Cathode Bypass ValveCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3562 concerns cathode bypass valve. Learn what this fault indicates and where to begin diagnosis.U3563Cathode Bypass Valve Position Sensor CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3563 concerns cathode bypass valve position sensor circuit. Learn what this fault indicates and where to begin diagnosis.U3564Hydrogen Supply Line A Pressure Sensor 1 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3564 concerns hydrogen supply line a pressure sensor 1 circuit. Learn what this fault indicates and where to begin diagnosis.U3565Hydrogen Supply Line A Pressure Sensor 2 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3565 concerns hydrogen supply line a pressure sensor 2 circuit. Learn what this fault indicates and where to begin diagnosis.U3566Anode Inlet Pressure Sensor 1 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3566 concerns anode inlet pressure sensor 1 circuit. Learn what this fault indicates and where to begin diagnosis.U3567Anode Inlet Pressure Sensor 2 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3567 concerns anode inlet pressure sensor 2 circuit. Learn what this fault indicates and where to begin diagnosis.U3568Anode Multifunction Valve Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3568 concerns anode multifunction valve control circuit. Learn what this fault indicates and where to begin diagnosis.U3569Anode Multifunction ValveCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3569 concerns anode multifunction valve. Learn what this fault indicates and where to begin diagnosis.U356AAnode Drain Valve Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356A concerns anode drain valve control circuit. Learn what this fault indicates and where to begin diagnosis.U356BAnode Drain ValveCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356B concerns anode drain valve. Learn what this fault indicates and where to begin diagnosis.U356CAnode Header Drain Valve Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356C concerns anode header drain valve control circuit. Learn what this fault indicates and where to begin diagnosis.U356DAnode Header Drain ValveCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356D concerns anode header drain valve. Learn what this fault indicates and where to begin diagnosis.U356EAnode Drain Valve Heater Relay Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356E concerns anode drain valve heater relay control circuit. Learn what this fault indicates and where to begin diagnosis.U356FAnode Header Drain Valve Heater Relay Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU356F concerns anode header drain valve heater relay control circuit. Learn what this fault indicates and where to begin diagnosis.U3570Stack Inlet Coolant Temperature Sensor CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3570 concerns stack inlet coolant temperature sensor circuit. Learn what this fault indicates and where to begin diagnosis.U3571Stack Outlet Coolant Temperature Sensor 1 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3571 concerns stack outlet coolant temperature sensor 1 circuit. Learn what this fault indicates and where to begin diagnosis.U3572Stack Outlet Coolant Temperature Sensor 2 CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3572 concerns stack outlet coolant temperature sensor 2 circuit. Learn what this fault indicates and where to begin diagnosis.U3573Coolant Mixing Valve Control CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3573 concerns coolant mixing valve control circuit. Learn what this fault indicates and where to begin diagnosis.U3574Coolant Mixing ValveCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3574 concerns coolant mixing valve. Learn what this fault indicates and where to begin diagnosis.U3575Coolant Mixing Valve Position Sensor CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3575 concerns coolant mixing valve position sensor circuit. Learn what this fault indicates and where to begin diagnosis.U3576Stack Differential Pressure Sensor CircuitCheck soonNetwork & Communication45–120 minutes for initial diagnosisU3576 concerns stack differential pressure sensor circuit. Learn what this fault indicates and where to begin diagnosis.U0002High Speed CAN Communication Bus PerformanceCheck soonNetwork & Communication45–120 minutes for initial diagnosisU0002 means High Speed CAN Communication Bus Performance. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.U0003High Speed CAN Communication Bus Positive OpenCheck soonNetwork & Communication45–120 minutes for initial diagnosisU0003 means High Speed CAN Communication Bus Positive Open. Review likely symptoms, causes, safety considerations, and a sensible diagnostic order.