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Diagnostic Codes List

This page provides a structured reference list of automotive Diagnostic Trouble Codes (DTCs) used by modern vehicle onboard diagnostic systems.

Diagnostic codes are generated by the ECU when a fault is detected in the engine, transmission, emissions system, vehicle network, or other electronic control systems. Each code represents a specific fault condition and serves as the starting point for vehicle diagnostics and troubleshooting.

This Diagnostic Codes List allows technicians and automotive professionals to browse fault codes by system category, quickly identify code meanings, and access detailed diagnostic information for each individual code.

By selecting a specific diagnostic code, you can view in-depth explanations including fault descriptions, affected systems, common causes, diagnostic procedures, and recommended inspection steps based on real-world diagnostic scenarios.

This list is designed to support efficient fault identification and accurate diagnosis using professional diagnostic tools, live data analysis, and vehicle-specific diagnostic workflows.

Select by System

P0456

Diagnostic trouble code P0456 indicates a small leak in the EVAP system

P0457

Diagnostic trouble code P0457 indicates a loose or missing fuel cap

P0460

Diagnostic trouble code P0460 indicates a malfunction in the fuel level sensor circuit

P0461

Diagnostic trouble code P0461 indicates a malfunction in the fuel level sensor range

P0464

Diagnostic trouble code P0464 indicates a malfunction in the fuel level sensor circuit

P0474

Diagnostic trouble code P0474 indicates an exhaust pressure sensor circuit malfunction

P0476

Diagnostic trouble code P0476 indicates a malfunction in the exhaust pressure sensor performance

P0477

Diagnostic trouble code P0477 indicates a malfunction in the exhaust pressure sensor

P0478

Diagnostic trouble code P0478 indicates an exhaust pressure sensor circuit range issue

P0491

Diagnostic trouble code P0491 indicates insufficient EGR flow detected in the exhaust system

P0492

Diagnostic trouble code P0492 indicates insufficient EGR flow detected in the exhaust system (Bank 2)

P0493

Diagnostic trouble code P0493 indicates a malfunction in the EGR pressure sensor

P0500

Diagnostic trouble code P0500 indicates a malfunction in the vehicle speed sensor circuit

P0501

Diagnostic trouble code P0501 indicates a malfunction in the vehicle speed sensor range

P0502

Diagnostic trouble code P0502 indicates low input from the vehicle speed sensor circuit

P0508

Diagnostic trouble code P0508 indicates a malfunction in the idle air control valve circuit

P0509

Diagnostic trouble code P0509 indicates an idle air control valve circuit range problem

P0511

Diagnostic trouble code P0511 indicates an idle air control valve performance issue

P0512

Diagnostic trouble code P0512 indicates an idle air control valve circuit malfunction

P0513

Diagnostic trouble code P0513 indicates an incorrect key code detected

P0525

Diagnostic trouble code P0525 indicates a malfunction in the fuel pressure sensor circuit

P0526

Diagnostic trouble code P0526 indicates an issue with the cooling fan speed control circuit

P0527

Diagnostic trouble code P0527 indicates an exhaust pressure sensor malfunction

P0528

Diagnostic trouble code P0528 indicates an issue with the engine cooling fan relay circuit

P0529

Diagnostic trouble code P0529 indicates a malfunction in the fuel pressure sensor circuit range

P0531

Diagnostic trouble code P0531 indicates a low input from the A/C refrigerant pressure sensor

P0534

Diagnostic trouble code P0534 indicates a refrigerant pressure sensor performance issue

P0535

Diagnostic trouble code P0535 indicates a malfunction in the A/C refrigerant temperature sensor circuit

P0536

Diagnostic trouble code P0536 indicates low input from the A/C refrigerant temperature sensor

P0537

Diagnostic trouble code P0537 indicates high input from the A/C refrigerant temperature sensor

P0538

Diagnostic trouble code P0538 indicates an intermittent fault in the A/C refrigerant temperature sensor circuit

P0539

Diagnostic trouble code P0539 indicates a malfunction in the A/C refrigerant pressure sensor circuit

P0551

Diagnostic trouble code P0551 indicates a malfunction in the power steering pressure sensor circuit

P0552

Diagnostic trouble code P0552 indicates low input from the power steering pressure sensor

P0553

Diagnostic trouble code P0553 indicates a high input from the power steering pressure sensor

P0554

Diagnostic trouble code P0554 indicates an intermittent fault in the power steering pressure sensor circuit

P0555

Diagnostic trouble code P0555 indicates a malfunction in the power steering assist system

P0556

Diagnostic trouble code P0556 indicates a malfunction in the power steering pressure sensor circuit

P0557

Diagnostic trouble code P0557 indicates low input from the power steering pressure sensor

P0558

Diagnostic trouble code P0558 indicates high input from the power steering pressure sensor

P0559

Diagnostic trouble code P0559 indicates an intermittent fault in the power steering pressure sensor circuit

P0560

Diagnostic trouble code P0560 indicates a malfunction in the system voltage

P0562

Diagnostic trouble code P0562 indicates low system voltage

P0563

Diagnostic trouble code P0563 indicates a malfunction in the system voltage range

P0564

Diagnostic trouble code P0564 indicates a malfunction in the system voltage circuit

P0565

Diagnostic trouble code P0565 indicates a malfunction in the ignition switch circuit

P0566

Diagnostic trouble code P0566 indicates an issue with the ignition system voltage

P0567

Diagnostic trouble code P0567 indicates a malfunction in the system voltage feedback circuit

P0568

Diagnostic trouble code P0568 indicates a malfunction in the voltage regulation circuit

P0591

Diagnostic trouble code P0591 indicates an issue with the cooling system thermostat control circuit

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