Powertrain, generic · Auxiliary emission controls

P0477 Exhaust Pressure Control Valve A Low

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

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.

Likely causes

Control wire shorted to ground

Flap actuator faulty internally

Flap seized by corrosion (motor blocked)

Chafed wire at the underbody

Symptoms

Check engine light on
Flap without function: sound unchanged, rattling
Diesel: longer warm-up, exhaust brake weak or EGR faults

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€150–900

Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

exhaust pressure control valve avalve actuatoractuator wiringengine control module

Related codes

P0475 P0478 P047F P048A P04A1

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.