P0471

What it means

P0471 means the engine control unit has found that the signal from exhaust pressure sensor A is not plausible. The reading is outside the expected range or does not change as it should when compared with engine load, speed, barometric pressure and other sensor data. The sensor is usually fitted on diesels and turbocharged engines, though its location and use depend on the model and engine.

Symptoms

• Engine warning light on
• Reduced power or the engine going into limp mode
• Poor or hesitant acceleration
• Turbocharger or variable geometry control not behaving normally
• Increased smoke or higher fuel consumption
• Particulate filter regeneration problems on some models

Possible causes

• Blocked, sooted or leaking sensor pipe or port, where the sensor is fed by a hose or tubelikely
• Faulty exhaust pressure sensor giving a drifting or stuck signallikely
• Damaged wiring, poor connector contact or corrosion in the sensor supply, ground or signal circuitlikely
• Exhaust leak near the sensor, or a restriction in the exhaust such as a clogged filter or catalyst, giving readings that do not match the engine's expected valuespossible
• Turbocharger or boost control fault (for example a sticking vane mechanism or wastegate) causing real pressure to differ from what is expectedpossible
• Faulty engine control unit or outdated software calibration, where a manufacturer bulletin identifies itrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting engine load, speed and temperature when the fault set. Check for related boost, particulate filter or pressure codes.
2. Visually inspect the sensor, its connector and wiring for heat damage, chafing, corrosion, oil or water ingress.
3. Check for exhaust leaks around the manifold, turbocharger, sensor and joints, and inspect any sensor pipe or hose for splits, blockage or soot build-up.
4. With the engine off and then running, view the live exhaust pressure value. Compare it with barometric pressure at key on and check it responds sensibly to throttle changes.
5. Check the sensor supply voltage, ground and signal at the connector against the manufacturer's specification for that model.
6. Test the wiring for continuity, shorts to ground, shorts to supply and high resistance between the sensor and control unit.
7. Check for a restricted exhaust or particulate filter by looking at differential pressure data and following the manufacturer's procedure for the engine.
8. Check for any software updates or technical bulletins for the vehicle before considering the control unit.

How to fix

• Clear or replace a blocked, split or loose sensor pipe or hose as required.
• Replace the exhaust pressure sensor if its signal is faulty or out of specification.
• Repair or replace damaged wiring and connectors, and clean or renew corroded terminals.
• Repair any exhaust leaks and replace damaged gaskets or components.
• Repair the turbocharger or boost control fault, or address a restricted filter or catalyst following the manufacturer's procedure.
• Update the control unit software only where an outdated or faulty calibration is a known cause for that vehicle.

Can I keep driving?

Nearby codes

• P0470GenericExhaust Pressure Sensor A Circuit
• P0472GenericExhaust Pressure Sensor A Circuit Low