OBD-II code · Powertrain (generic)
P0478 Exhaust Pressure Control Valve A High
Exhaust pressure control valve A drive line stuck high — short to B+.
Is it safe to drive with P0478?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyShort to B+
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.7–3 h
- Emissions test
- Likely to fail
- Parts involved
- Exhaust Pressure Regulator
Related codes
- P0475Exhaust Pressure Control Valve A
- P04A2Exhaust Pressure Control Valve B High
- P0476Exhaust Pressure Control Valve A Range/Performance
- P0477Exhaust Pressure Control Valve A Low
- P0479Exhaust Pressure Control Valve A Intermittent
- P047AExhaust Pressure Sensor B Circuit
- P047BExhaust Pressure Sensor B Circuit Range/Performance
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.