What it means
Exhaust pressure control valve A is mechanically stuck open — backpressure cannot be raised, exhaust brake and DPF regen support fail.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Exhaust pressure control valve A restricts exhaust flow to raise backpressure for exhaust braking or DPF support on vehicles equipped with those functions. The control module sets P047F when it detects that valve A is stuck open and cannot close enough to create the expected restriction.
Common causes
Most likely first.
- Carbon buildup or broken return spring
- Carbon or debris buildup preventing free movement
- Component wear with age - mechanical play
Symptoms
- Check-engine light on
- Reduced exhaust-brake performance, if equipped
- Possible reduced engine power
- DPF regeneration problems or warning, where equipped
How to diagnose it
- Save freeze-frame data and check valve A command and position data, if available, to confirm the fault occurs when the valve should close.
- Inspect valve A and its linkage for visible damage, loose parts, or deposits that could prevent movement.
- Check the actuator and connector operation using the manufacturer’s procedure to confirm whether the valve is being commanded correctly.
- With the exhaust system safely cool, verify that valve A moves freely through its operating range as specified by the manufacturer.
- If the valve moves freely and its actuator circuit passes testing, check for a control or position-feedback fault.
Common fixes
- Remove carbon or debris that is preventing valve A from moving, if cleaning is approved for that part.
- Repair or replace a broken return spring or damaged linkage.
- Replace exhaust pressure control valve A if it is mechanically worn or remains stuck open.
- Repair the actuator or control circuit if testing shows it is not moving the valve correctly.
Can I keep driving?
Avoid relying on exhaust braking where fitted and use lower loads, especially on long descents. DPF regeneration may be impaired, and reduced power or worsening exhaust-control problems can follow.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.