PowertrainP0478
CautionSeverity: Caution - get it checked when you can
Exhaust Pressure Control Valve A High
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 · SAE J2012: the standard generic code list · 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 25
| Brand | Code | Description | System |
|---|---|---|---|
| Ashok Leyland CV | P0478 | Cylinder Head Temperature Sensor Brand | Powertrain |
| BAIC Motor | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| BMW | P0478 | Exhaust Press. Contr. Valve High Brand | Powertrain |
| BYD | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Chery | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Daewoo | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| DFFS | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| DFFX | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| DFXK | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| EOBD | P0478 | Uitlaatdrukregelklep 'A' hoog Brand | Powertrain |
| Geely | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| GM | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Great Wall | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Hafei | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Holden | P0478 | Exhaust Pressure Control Valve A High SAE | Powertrain |
| Hyundai | P0478 | Exhaust Pressure Control Valve A High SAE | Powertrain |
| Isuzu | P0478 | Exhaust Pressure Control Valve A High SAE | Powertrain |
| Land Rover | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Maserati | P0478 | Exhaust pressure control valve a high Brand | Powertrain |
| Opel | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Peugeot | P0478 | Exhaust Pressure Control Valve A High SAE | Powertrain |
| Saab | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| MG (SAIC) | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Tata | P0478 | Exhaust Pressure Control Valve High Brand | Powertrain |
| Toyota | P0478 | Exhaust Pressure Control Valve High 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.
5Extended variant codes 2
These 7-character codes are manufacturer-specific variants of P0478 and may be reported by some scan tools.
| Brand | Code | Description | System |
|---|---|---|---|
| Porsche | P047800 | No description available | Powertrain |
| Volkswagen | P047800 | Exhaust Pressure Control Valve 'A' High Brand | Powertrain |
6Related codes
Browse Pxxx codes or P047xx codes.