P0477Exhaust Pressure Control Valve A Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- The exhaust pressure control valve is a flap in the exhaust: on older Navistar/Ford diesels a warm-up flap that raises back pressure when cold, on Ram and others an exhaust brake, on VW's 2.0 TDI a flap that drives the low-pressure EGR, and on Audi and Bentley a sound flap. P0477 means the control circuit of valve A is low. Audi uses it for a short to ground of the exhaust flap. VW's 2.0 TDI of 2009–12 sets it together with P047F, P048A–P048C and P0401 when salt has corroded the flap shaft and the flap sticks – a blocked motor can cause overcurrent or a voltage drop; on the 2015 engine it appears with P0478/P0475 and the actuator is replaced.
- What you may notice
- Check engine light on
- Flap without function: sound unchanged, rattling
- Diesel: longer warm-up, exhaust brake weak or EGR faults
- Likely causes
- LikelyControl wire shorted to ground
- LikelyFlap actuator faulty internally
- PossibleFlap seized by corrosion (motor blocked)
- PossibleChafed wire at the underbody
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €150 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.