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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

P0482

Diagnostic trouble code P0482 indicates a malfunction in cooling fan 3 control circuit

P0483

Diagnostic trouble code P0483 indicates a cooling fan rationality check failure

P0494

Diagnostic trouble code P0494 indicates low speed operation detected in the cooling fan system

P0495

Diagnostic trouble code P0495 indicates high speed operation detected in the cooling fan system

P0523

Diagnostic trouble code P0523 indicates high input from the engine oil pressure sensor

P0530

Diagnostic trouble code P0530 indicates an A/C refrigerant pressure sensor circuit malfunction

P0532

Diagnostic trouble code P0532 indicates low input from the A/C refrigerant pressure sensor

P0533

Diagnostic trouble code P0533 indicates high input from the A/C refrigerant pressure sensor

P0540

Diagnostic trouble code P0540 indicates an intake air heater circuit malfunction

P0400

Diagnostic trouble code P0400 indicates a general exhaust gas recirculation (EGR) flow malfunction

P0401

Diagnostic trouble code P0401 indicates insufficient EGR flow detected

P0402

Diagnostic trouble code P0402 indicates excessive EGR flow detected

P0403

Diagnostic trouble code P0403 indicates a malfunction in the EGR control circuit

P0412

Diagnostic trouble code P0412 indicates a malfunction in the secondary air injection switching valve A circuit

P0413

Diagnostic trouble code P0413 indicates an open circuit in the secondary air injection valve

P0414

Diagnostic trouble code P0414 indicates a short circuit in the secondary air injection valve

P0415

Diagnostic trouble code P0415 indicates a malfunction in the secondary air injection switching valve B circuit

P0420

Diagnostic trouble code P0420 indicates catalyst system efficiency below threshold (Bank 1)

P0430

Diagnostic trouble code P0430 indicates catalyst system efficiency below threshold (Bank 2)

P0442

Diagnostic trouble code P0442 indicates a small leak detected in the EVAP system

P0446

Diagnostic trouble code P0446 indicates a malfunction in the EVAP vent control circuit

P0455

Diagnostic trouble code P0455 indicates a large leak detected in the EVAP system

P0087

Diagnostic trouble code P0087 indicates fuel rail or system pressure is too low

P0088

Diagnostic trouble code P0088 indicates fuel rail or system pressure is too high

P0089

Diagnostic trouble code P0089 indicates fuel pressure regulator performance issues

P0090

Diagnostic trouble code P0090 indicates a malfunction in the fuel pressure regulator control circuit

P0091

Diagnostic trouble code P0091 indicates low input in the fuel pressure regulator control circuit

P0092

Diagnostic trouble code P0092 indicates high input in the fuel pressure regulator control circuit

P0200

Diagnostic trouble code P0200 indicates an injector circuit malfunction

P0201

Diagnostic trouble code P0201 indicates a malfunction in injector circuit cylinder 1

P0202

Diagnostic trouble code P0202 indicates a malfunction in injector circuit cylinder 2

P0203

Diagnostic trouble code P0203 indicates a malfunction in injector circuit cylinder 3

P0204

Diagnostic trouble code P0204 indicates a malfunction in injector circuit cylinder 4

P0210

Diagnostic trouble code P0210 indicates a malfunction in injector circuit cylinder 10

U0100

Diagnostic trouble code U0100 indicates lost communication with the engine control module (ECM/PCM)

U0101

Diagnostic trouble code U0101 indicates lost communication with the transmission control module (TCM)

U0102

Diagnostic trouble code U0102 indicates lost communication with the transfer case control module

U0103

Diagnostic trouble code U0103 indicates lost communication with the gear shift module

U0105

Diagnostic trouble code U0105 indicates lost communication with the fuel injector control module

U0121

Diagnostic trouble code U0121 indicates lost communication with the ABS control module

U0126

Diagnostic trouble code U0126 indicates lost communication with the steering angle sensor module

U0129

Diagnostic trouble code U0129 indicates lost communication with the brake system control module

U0140

Diagnostic trouble code U0140 indicates lost communication with the body control module (BCM)

U0142

Diagnostic trouble code U0142 indicates lost communication with body control module C

U0146

Diagnostic trouble code U0146 indicates lost communication with the gateway module

U0151

Diagnostic trouble code U0151 indicates lost communication with the restraints control module (airbag)

U0155

Diagnostic trouble code U0155 indicates lost communication with the instrument cluster

U0171

Diagnostic trouble code U0171 indicates lost communication with the restraint system sensor

U0199

Diagnostic trouble code U0199 indicates lost communication with the door control module

U0293

Diagnostic trouble code U0293 indicates lost communication with the hybrid powertrain control module

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