P0476

What it means

P0476 is the generic SAE J2012 code for an exhaust pressure control valve performance fault. The engine control unit has seen that the actual exhaust pressure does not match the target it is commanding through the valve, or that the valve is not moving as expected. The valve is typically used on diesel engines, for example in turbocharger or exhaust braking systems, but the layout varies by model and engine.

Symptoms

• Engine warning light on
• Reduced power or the car going into limp mode
• Poor or uneven turbocharger boost response
• Black or excessive exhaust smoke
• Increased fuel consumption
• Rough running or hesitation under load

Possible causes

• Exhaust pressure control valve stuck or sluggish due to soot and carbon build-uplikely
• Faulty or damaged wiring, connectors or poor earth to the valve or its actuatorlikely
• Faulty exhaust pressure sensor or blocked sensor pipe giving a false readinglikely
• Exhaust leak before the valve or sensor upsetting the pressure readingpossible
• Failed valve actuator, vacuum supply fault or control solenoid, depending on how the system is operatedpossible
• Restricted exhaust, for example a clogged particulate filter or catalyst, causing abnormal pressurepossible
• Internal control unit fault or outdated software where the manufacturer has a known issuerare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting load, engine speed and temperature when the fault set, and check for related boost, particulate filter or sensor codes.
2. Visually inspect the valve, actuator, wiring, connectors and any vacuum hoses for damage, heat damage, corrosion or looseness.
3. Check for exhaust leaks around the manifold, turbocharger, valve and joints upstream of the pressure sensor.
4. Compare live data for commanded versus actual valve position and exhaust pressure at idle and under load, following the manufacturer's procedure for your model.
5. Use a bidirectional test to command the valve open and closed and check that it moves smoothly and the position feedback follows.
6. Test the sensor supply, signal and earth circuits and check the sensor pipe is clear, where fitted.
7. Check the valve electrical supply, control signal and, if vacuum operated, the vacuum supply as per the workshop data for the engine.
8. Check exhaust back pressure and particulate filter condition if the valve and sensor test correctly.

How to fix

• Clean or replace the exhaust pressure control valve if it is seized or sticking, in line with the manufacturer's guidance.
• Repair or replace damaged wiring, connectors or earth connections.
• Replace the exhaust pressure sensor or clear its pipe if blocked.
• Repair any exhaust leaks and renew faulty gaskets.
• Replace the actuator, solenoid or vacuum components if they fail testing, then carry out any required adaptation or relearn.
• Address any exhaust restriction using the manufacturer's approved procedure, and apply a software update only if a known fault in the calibration is documented.

Can I keep driving?

Nearby codes

• P0475GenericExhaust Pressure Control Valve A
• P0477GenericExhaust Pressure Control Valve A Low