P04xx OBD-II Codes (P0400–P0499)
100 fault codes in the P04xx range. Click any code for causes, diagnostic steps, severity, and common fixes.
P0400 moderate
Exhaust Gas Recirculation Flow Malfunction
P0401 moderate
Exhaust Gas Recirculation Flow Insufficient Detected
P0402 moderate
Exhaust Gas Recirculation Flow Excessive Detected
P0403 moderate
Exhaust Gas Recirculation Circuit Malfunction
P0404 moderate
Exhaust Gas Recirculation Circuit Range/Performance
P0405 moderate
Exhaust Gas Recirculation Sensor A Circuit Low
P0406 moderate
Exhaust Gas Recirculation Sensor A Circuit High
P0407 moderate
Exhaust Gas Recirculation Sensor B Circuit Low
P0408 moderate
Exhaust Gas Recirculation Sensor B Circuit High
P0409 moderate
Exhaust Gas Recirculation Sensor A Circuit Intermittent
P0410 moderate
Secondary Air Injection System Malfunction
P0411 moderate
Secondary Air Injection System Incorrect Flow Detected
P0412 low
Secondary Air Injection System Switching Valve A Circuit Malfunction
P0413 low
Secondary Air Injection System Switching Valve A Circuit Open
P0414 low
Secondary Air Injection System Switching Valve A Circuit Shorted
P0415 low
Secondary Air Injection System Switching Valve B Circuit Malfunction
P0416 low
Secondary Air Injection System Switching Valve B Circuit Open
P0417 low
Secondary Air Injection System Switching Valve B Circuit Shorted
P0418 low
Secondary Air Injection System Relay A Circuit Malfunction
P0419 low
Secondary Air Injection System Relay B Circuit Malfunction
P0420 moderate
Catalyst System Efficiency Below Threshold (Bank 1)
P0421 moderate
Warm Up Catalyst Efficiency Below Threshold (Bank 1)
P0422 moderate
Main Catalyst Efficiency Below Threshold (Bank 1)
P0423 moderate
Heated Catalyst Efficiency Below Threshold (Bank 1)
P0424 moderate
Heated Catalyst Temperature Below Threshold (Bank 1)
P0425 low
Catalyst Temperature Sensor (Bank 1)
P0426 low
Catalyst Temperature Sensor Range/Performance (Bank 1)
P0427 low
Catalyst Temperature Sensor Low (Bank 1)
P0428 moderate
Catalyst Temperature Sensor High (Bank 1)
P0429 low
Catalyst Heater Control Circuit (Bank 1)
P0430 moderate
Catalyst System Efficiency Below Threshold (Bank 2)
P0431 moderate
Warm Up Catalyst Efficiency Below Threshold (Bank 2)
P0432 moderate
Main Catalyst Efficiency Below Threshold (Bank 2)
P0433 moderate
Heated Catalyst Efficiency Below Threshold (Bank 2)
P0434 moderate
Heated Catalyst Temperature Below Threshold (Bank 2)
P0435 low
Catalyst Temperature Sensor (Bank 2)
P0436 low
Catalyst Temperature Sensor Range/Performance (Bank 2)
P0437 low
Catalyst Temperature Sensor Low (Bank 2)
P0438 moderate
Catalyst Temperature Sensor High (Bank 2)
P0439 low
Catalyst Heater Control Circuit (Bank 2)
P0440 minor
Evaporative Emission Control System Malfunction
P0441 low
Evaporative Emission Control System Incorrect Purge Flow
P0442 minor
Evaporative Emission Control System Leak Detected (Small Leak)
P0443 minor
Evaporative Emission Control System Purge Control Valve Circuit Malfunction
P0444 low
Evaporative Emission Control System Purge Control Valve Circuit Open
P0445 low
Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0446 minor
Evaporative Emission Control System Vent Control Circuit Malfunction
P0447 low
Evaporative Emission Control System Vent Control Circuit Open
P0448 low
Evaporative Emission Control System Vent Control Circuit Shorted
P0449 minor
Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction
P0450 low
Evaporative Emission Control System Pressure Sensor Malfunction
P0451 low
Evaporative Emission Control System Pressure Sensor Range/Performance
P0452 low
Evaporative Emission Control System Pressure Sensor Low Input
P0453 low
Evaporative Emission Control System Pressure Sensor High Input
P0454 low
Evaporative Emission Control System Pressure Sensor Intermittent
P0455 moderate
Evaporative Emission Control System Leak Detected (Large Leak)
P0456 minor
Evaporative Emission Control System Leak Detected (Very Small Leak)
P0457 minor
Evaporative Emission Control System Leak Detected (Fuel Cap Loose/Off)
P0458 low
Evaporative Emission Control System Purge Control Valve Circuit Low
P0459 low
Evaporative Emission Control System Purge Control Valve Circuit High
P0460 low
Fuel Level Sensor Circuit
P0461 low
Fuel Level Sensor Circuit Range/Performance
P0462 low
Fuel Level Sensor Circuit Low
P0463 low
Fuel Level Sensor Circuit High
P0464 low
Fuel Level Sensor Circuit Intermittent
P0465 low
EVAP Purge Flow Sensor Circuit
P0466 low
EVAP Purge Flow Sensor Circuit Range/Performance
P0467 low
EVAP Purge Flow Sensor Circuit Low
P0468 low
EVAP Purge Flow Sensor Circuit High
P0469 low
EVAP Purge Flow Sensor Circuit Intermittent
P0470 moderate
Exhaust Pressure Sensor Circuit
P0471 moderate
Exhaust Pressure Sensor Circuit Range/Performance
P0472 moderate
Exhaust Pressure Sensor Circuit Low
P0473 moderate
Exhaust Pressure Sensor Circuit High
P0474 moderate
Exhaust Pressure Sensor Circuit Intermittent
P0475 moderate
Exhaust Pressure Control Valve Circuit
P0476 moderate
Exhaust Pressure Control Valve Circuit Range/Performance
P0477 moderate
Exhaust Pressure Control Valve Circuit Low
P0478 moderate
Exhaust Pressure Control Valve Circuit High
P0479 moderate
Exhaust Pressure Control Valve Circuit Intermittent
P0480 critical
Cooling Fan 1 Control Circuit Malfunction
P0481 critical
Cooling Fan 2 Control Circuit Malfunction
P0482 critical
Cooling Fan 3 Control Circuit Malfunction
P0483 moderate
Cooling Fan Rationality Check Malfunction
P0484 critical
Cooling Fan Circuit Over Current
P0485 critical
Cooling Fan Power/Ground Circuit Malfunction
P0486 moderate
Exhaust Gas Recirculation Sensor B Circuit
P0487 moderate
Exhaust Gas Recirculation Throttle Position Control Circuit
P0488 moderate
Exhaust Gas Recirculation Throttle Position Control Range/Performance
P0489 moderate
Exhaust Gas Recirculation Control Circuit Low
P0490 moderate
Exhaust Gas Recirculation Control Circuit High
P0491 low
Secondary Air Injection System Insufficient Flow (Bank 1)
P0492 low
Secondary Air Injection System Insufficient Flow (Bank 2)
P0493 moderate
Fan Overspeed - Bank 1
P0494 moderate
Fan Speed Low - Bank 1
P0495 low
Fan Speed High - Bank 1
P0496 low
Evaporative Emission System High Purge Flow
P0497 low
Evaporative Emission System Low Purge Flow
P0498 low
Evaporative Emission System Vent Valve Control Circuit Low
P0499 low
Evaporative Emission System Vent Valve Control Circuit High