OBD2 · Powertrain
P04xx codes: emission controls — EGR, secondary air, catalyst, EVAP
101 codes in this range, all generic — the same meaning on every make. The systems that clean up exhaust and fuel vapor: exhaust gas recirculation (EGR), secondary air injection, catalytic converter monitoring, the evaporative emissions (EVAP) system with its purge and vent valves — plus exhaust temperature sensors, the particulate filter and some cooling-fan circuits.
What usually causes codes in this area
- A loose or faulty gas cap and other EVAP leaks
- Carbon-clogged EGR valves and passages
- Worn catalytic converters or lazy oxygen sensors
- Stuck purge and vent valves
Can you keep driving?
Most codes here don’t change how the car drives — you can keep going and fix it before the next emissions test. The exceptions are the cooling-fan codes (watch the temperature gauge), particulate-filter codes on diesels, and anything that comes with a flashing lamp or a rotten-egg smell.
All P04xx codes
| Code | Meaning |
|---|---|
| P0400 | Exhaust Gas Recirculation Flow |
| P0401 | Exhaust Gas Recirculation Flow Insufficient Detected |
| P0402 | Exhaust Gas Recirculation Flow Excessive Detected |
| P0403 | Exhaust Gas Recirculation Control Circuit |
| P0404 | Exhaust Gas Recirculation Circuit Range/Performance |
| P0405 | Exhaust Gas Recirculation Sensor "A" Circuit Low |
| P0406 | Exhaust Gas Recirculation Sensor "A" Circuit High |
| P0407 | Exhaust Gas Recirculation Sensor "B" Circuit Low |
| P0408 | Exhaust Gas Recirculation Sensor "B" Circuit High |
| P0409 | Exhaust Gas Recirculation Sensor "A" Circuit |
| P0410 | Secondary Air Injection System |
| P0411 | Secondary Air Injection System Incorrect Flow Detected |
| P0412 | Secondary Air Injection System Switching Valve "A" Circuit |
| P0413 | Secondary Air Injection System Switching Valve "A" Circuit Open |
| P0414 | Secondary Air Injection System Switching Valve "A" Circuit Shorted |
| P0415 | Secondary Air Injection System Switching Valve "B" Circuit |
| P0416 | Secondary Air Injection System Switching Valve "B" Circuit Open |
| P0417 | Secondary Air Injection System Switching Valve "B" Circuit Shorted |
| P0418 | Secondary Air Injection System Relay "A" Circuit |
| P0419 | Secondary Air Injection System Control "B" Circuit |
| P0420 | Catalyst System Efficiency Below Threshold (Bank 1) |
| P0421 | Warm Up Catalyst Efficiency Below Threshold (Bank 1) |
| P0422 | Main Catalyst Efficiency Below Threshold (Bank 1) |
| P0423 | Heated Catalyst Efficiency Below Threshold (Bank 1) |
| P0424 | Heated Catalyst Temperature Below Threshold (Bank 1) |
| P0425 | Catalyst Temperature Sensor (Bank 1) |
| P0426 | Catalyst Temperature Sensor Range/Performance (Bank 1) |
| P0427 | Catalyst Temperature Sensor Low (Bank 1, Sensor 1) |
| P0428 | Catalyst Temperature Sensor High (Bank 1, Sensor 1) |
| P0429 | Catalyst Heater Control Circuit (Bank 1) |
| P0430 | Catalyst System Efficiency Below Threshold (Bank 2) |
| P0431 | Warm Up Catalyst Efficiency Below Threshold (Bank 2) |
| P0432 | Main Catalyst Efficiency Below Threshold (Bank 2) |
| P0433 | Heated Catalyst Efficiency Below Threshold (Bank 2) |
| P0434 | Heated Catalyst Temperature Below Threshold (Bank 2) |
| P0435 | Catalyst Temperature Sensor (Bank 2, Sensor 1) |
| P0436 | Catalyst Temperature Sensor Range/Performance (Bank 2, Sensor 1) |
| P0437 | Catalyst Temperature Sensor Low (Bank 2, Sensor 1) |
| P0438 | Catalyst Temperature Sensor High (Bank 2, Sensor 1) |
| P0439 | Catalyst Heater Control Circuit (Bank 2) |
| P0440 | Evaporative Emission System |
| P0441 | Evaporative Emission System Incorrect Purge Flow |
| P0442 | Evaporative Emission System Leak Detected (Small Leak) |
| P0443 | Evaporative Emission System Purge Control Valve Circuit |
| P0444 | Evaporative Emission System Purge Control Valve Circuit Open |
| P0445 | Evaporative Emission System Purge Control Valve Circuit Shorted |
| P0446 | Evaporative Emission System Vent Control Circuit |
| P0447 | Evaporative Emission System Vent Control Circuit Open |
| P0448 | Evaporative Emission System Vent Control Circuit Shorted |
| P0449 | Evaporative Emission System Vent Valve/Solenoid Circuit |
| P0450 | Evaporative Emission System Pressure Sensor/Switch |
| P0451 | Evaporative Emission System Pressure Sensor/Switch Range/Performance |
| P0452 | Evaporative Emission System Pressure Sensor/Switch Low |
| P0453 | Evaporative Emission System Pressure Sensor/Switch High |
| P0454 | Evaporative Emission System Pressure Sensor/Switch Intermittent |
| P0455 | Evaporative Emission System Leak Detected (Large Leak) |
| P0456 | Evaporative Emission System Leak Detected (Very Small Leak) |
| P0457 | Evaporative Emission System Leak Detected (Fuel Cap Loose/Off) |
| P0458 | Evaporative Emission System Purge Control Valve Circuit Low |
| P0459 | Evaporative Emission System Purge Control Valve Circuit High |
| P0460 | Fuel Level Sensor "A" Circuit |
| P0461 | Fuel Level Sensor "A" Circuit Range/Performance |
| P0462 | Fuel Level Sensor "A" Circuit Low |
| P0463 | Fuel Level Sensor "A" Circuit High |
| P0464 | Fuel Level Sensor "A" Circuit Intermittent |
| P0465 | Evaporative Emission System Purge Flow Sensor Circuit |
| P0466 | Evaporative Emission System Purge Flow Sensor Circuit Range/Performance |
| P0467 | Evaporative Emission System Purge Flow Sensor Circuit Low |
| P0468 | Evaporative Emission System Purge Flow Sensor Circuit High |
| P0469 | Evaporative Emission System Purge Flow Sensor Circuit Intermittent |
| P0470 | Exhaust Pressure Sensor "A" Circuit |
| P0471 | Exhaust Pressure Sensor "A" Circuit Range/Performance |
| P0472 | Exhaust Pressure Sensor "A" Circuit Low |
| P0473 | Exhaust Pressure Sensor "A" Circuit High |
| P0474 | Exhaust Pressure Sensor "A" Circuit Intermittent |
| P0475 | Exhaust Pressure Control Valve "A" |
| P0476 | Exhaust Pressure Control Valve "A" Range/Performance |
| P0477 | Exhaust Pressure Control Valve "A" Low |
| P0478 | Exhaust Pressure Control Valve "A" High |
| P0479 | Exhaust Pressure Control Valve "A" Intermittent |
| P0480 | Fan 1 Control Circuit |
| P0481 | Fan 2 Control Circuit |
| P0482 | Fan 3 Control Circuit |
| P0483 | Cooling Fan Rationality Check |
| P0484 | Fan Circuit Over Current |
| P0485 | Fan Power/Ground Circuit |
| P0486 | Exhaust Gas Recirculation Sensor "B" Circuit |
| P0487 | Exhaust Gas Recirculation Throttle Position Control Circuit |
| P0488 | Exhaust Gas Recirculation Throttle Position Control Range/Performance |
| P0489 | Exhaust Gas Recirculation "A" Control Circuit Low |
| P0490 | Exhaust Gas Recirculation "A" Control Circuit High |
| P0491 | Secondary Air Injection System Insufficient Flow (Bank 1) |
| P0492 | Secondary Air Injection System Insufficient Flow (Bank 2) |
| P0493 | Fan Overspeed |
| P0494 | Fan Speed Low |
| P0495 | Fan Speed High |
| P0496 | Evaporative Emission System High Purge Flow |
| P0497 | Evaporative Emission System Low Purge Flow |
| P0498 | Evaporative Emission System Vent Valve Control Circuit Low |
| P0499 | Evaporative Emission System Vent Valve Control Circuit High |
| P04DB | Crankcase Ventilation System Disconnected |
Read the codes from your own car
Plug an inexpensive Bluetooth LE or Wi-Fi OBD2 adapter into the port under the dashboard, and Brimly on your iPhone reads the stored, pending and permanent codes, explains each one offline and clears them once the fault is fixed. OBD diagnostics are part of Brimly Forever, a one-time purchase.
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