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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

P0592

Diagnostic trouble code P0592 indicates a malfunction in the cooling system thermostat

P0593

Diagnostic trouble code P0593 indicates an intermittent fault in the cooling system thermostat control circuit

P0594

Diagnostic trouble code P0594 indicates an issue with the thermostat heater control circuit

P0595

Diagnostic trouble code P0595 indicates a thermostat stuck open

P0596

Diagnostic trouble code P0596 indicates a thermostat stuck closed

P0597

Diagnostic trouble code P0597 indicates a malfunction in the cooling system thermostat bypass control

P0600

Diagnostic trouble code P0600 indicates a malfunction in the communication between the ECM and the TCM

P0601

Diagnostic trouble code P0601 indicates an internal failure within the ECM

P0602

Diagnostic trouble code P0602 indicates a problem with the ECM's programming

P0603

Diagnostic trouble code P0603 indicates an EEPROM malfunction in the ECM

P0604

Diagnostic trouble code P0604 indicates a malfunction in the ECM's internal processor

P0605

Diagnostic trouble code P0605 indicates a problem with the ECM’s processor memory

P0606

Diagnostic trouble code P0606 indicates a malfunction in the ECM’s processor circuit

P0607

Diagnostic trouble code P0607 indicates a problem with the ECM’s internal circuit

P0608

Diagnostic trouble code P0608 indicates an internal fault in the ECM's memory

P0609

Diagnostic trouble code P0609 indicates a problem with the ECM's voltage regulation

P0610

Diagnostic trouble code P0610 indicates a malfunction in the ECM's cooling system

P0611

Diagnostic trouble code P0611 indicates an internal fault in the ECM's control system

P0612

Diagnostic trouble code P0612 indicates a malfunction in the ECM's power supply

P0620

Diagnostic trouble code P0620 indicates a malfunction in the alternator control circuit

P0621

Diagnostic trouble code P0621 indicates an issue with the alternator field control circuit

P0622

Diagnostic trouble code P0622 indicates a malfunction in the alternator control circuit

P0623

Diagnostic trouble code P0623 indicates a malfunction in the fuel pump control circuit

P0624

Diagnostic trouble code P0624 indicates an issue with the fuel pump relay control circuit

P0625

Diagnostic trouble code P0625 indicates a malfunction in the generator field circuit

P0626

Diagnostic trouble code P0626 indicates a malfunction in the fuel rail pressure sensor circuit

P0627

Diagnostic trouble code P0627 indicates a malfunction in the fuel pressure sensor circuit

P0628

Diagnostic trouble code P0628 indicates an issue with the fuel pressure regulator circuit

P0629

Diagnostic trouble code P0629 indicates an issue with the fuel injector control circuit

P0630

Diagnostic trouble code P0630 indicates an issue with the mass airflow sensor circuit

P0631

Diagnostic trouble code P0631 indicates an issue with the fuel rail pressure sensor circuit

P0632

Diagnostic trouble code P0632 indicates a malfunction in the fuel pressure sensor circuit

P0633

Diagnostic trouble code P0633 indicates a malfunction in the intake air temperature sensor circuit

P0634

Diagnostic trouble code P0634 indicates a malfunction in the intake air temperature sensor performance

P0635

Diagnostic trouble code P0635 indicates a malfunction in the intake manifold pressure sensor circuit

P0636

Diagnostic trouble code P0636 indicates an issue with the fuel injector circuit

P0637

Diagnostic trouble code P0637 indicates a malfunction in the fuel rail pressure sensor circuit

P0638

Diagnostic trouble code P0638 indicates an issue with the fuel pressure sensor circuit

P0639

Diagnostic trouble code P0639 indicates a malfunction in the engine coolant temperature sensor circuit

P0640

Diagnostic trouble code P0640 indicates an issue with the intake air temperature sensor circuit

P0641

Diagnostic trouble code P0641 indicates a malfunction in the intake air temperature sensor circuit

P0642

Diagnostic trouble code P0642 indicates a malfunction in the throttle position sensor circuit

P0643

Diagnostic trouble code P0643 indicates a malfunction in the exhaust gas temperature sensor circuit

P0644

Diagnostic trouble code P0644 indicates a malfunction in the fuel rail pressure sensor circuit

P0645

Diagnostic trouble code P0645 indicates a malfunction in the exhaust gas recirculation (EGR) control circuit

P0646

Diagnostic trouble code P0646 indicates a malfunction in the fuel pressure sensor circuit

P0647

Diagnostic trouble code P0647 indicates a malfunction in the intake air temperature sensor circuit

P0648

Diagnostic trouble code P0648 indicates a malfunction in the fuel pressure sensor circuit

P0649

Diagnostic trouble code P0649 indicates a malfunction in the air intake pressure sensor circuit

P0650

Diagnostic trouble code P0650 indicates a malfunction in the coolant temperature sensor circuit

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