PowertrainP04A4
CautionSeverity: Caution - get it checked when you can
Lock actuator cut-off relay unit failure (BCAP)
Key terms: Catalytic converter: cleans the exhaust gases · EGR: exhaust gas recirculation, which cuts harmful gases · EVAP: the system that traps fuel vapour · Oxygen sensor: measures oxygen in the exhaust gas · Powertrain: engine, transmission and emissions
1What it means in plain English
This range covers emissions control (EGR, EVAP, oxygen sensors and the catalytic converter), but some manufacturers also use P04 codes for oil-pressure, brake-fluid and coolant-level warnings.
2Common causes
- Clogged or faulty EGR valve
- EVAP system leak (hoses, canister, fuel cap)
- Faulty oxygen sensor
- Ageing catalytic converter
- Low oil, brake fluid or coolant (on some models)
- Wiring or connector fault
3Can I drive?
Do not assume this code is safe to drive. Check the description: if it names oil pressure, brake fluid, coolant, or a brake fault, stop safely and have it diagnosed before driving. Emissions-only codes (EGR, EVAP, catalyst) should still be checked before an emissions or roadworthiness inspection.
This page gives general information. It is not professional advice. For a definite diagnosis and a repair quote, ask a qualified mechanic to inspect the car.
4Brand data 20
| Brand | Code | Description | System |
|---|---|---|---|
| Ashok Leyland CV | P04A4 | No description available | Powertrain |
| BAIC Motor | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| BYD | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Chery | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| DFFS | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| DFFX | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| DFXK | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| EOBD | P04A4 | Uitlaatdrukregelklep 'B' vast open Brand | Powertrain |
| Geely | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| GM | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Great Wall | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Hafei | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Hyundai | P04A4 | No description available | Powertrain |
| Isuzu | P04A4 | No description available | Powertrain |
| Land Rover | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Peugeot | P04A4 | No description available | Powertrain |
| Saab | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| MG (SAIC) | P04A4 | Exhaust Pressure Control Valve 'B' Stuck Open Brand | Powertrain |
| Tata | P04A4 | No description available | Powertrain |
| Toyota | P04A4 | Lock actuator cut-off relay unit failure (BCAP) Brand | Powertrain |
Legend: SAE is the generic J2012 description; Brand is text taken from that manufacturer’s data. Manufacturer rows keep the wording and language of the source data, and non-English text is tagged so screen readers pronounce it correctly.
5Related codes
Browse Pxxx codes or P04Axx codes.