Damaged, chafed or corroded wiring to the exhaust pressure sensor, including open or high-resistance circuits; Loose, corroded or contaminated connector at the sensor or control unit; Faulty exhaust pressure sensor with an intermittent internal fault; Blocked, sooted or leaking sensor pipe or hose, where the sensor is connected by a pressure line; Exhaust leak near the sensor causing unstable readings; Sensor supply or ground fault caused by a problem elsewhere in the circuit; Fault within the engine control unit.

P0474

Exhaust Pressure Sensor A Circuit Intermittent/Erratic.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
74: FaultThe specific fault in that area

What it means

P0474 is the generic code for an intermittent or erratic signal in the exhaust pressure sensor 'A' circuit. The engine control unit saw the sensor's voltage or signal jump, drop out or behave implausibly compared with engine load, speed and other pressure readings. Exhaust pressure sensors are mainly fitted to turbocharged diesels and some petrol engines, and the exact location and layout depend on the model and engine.

Symptoms

Engine warning light on
Reduced power or the car going into limp mode
Poor or hesitant acceleration
Uneven turbo boost or erratic boost behaviour
Possible rough running or increased smoke on some diesels
Particulate filter regeneration problems on diesels with other related codes

Possible causes

Damaged, chafed or corroded wiring to the exhaust pressure sensor, including open or high-resistance circuitslikely
Loose, corroded or contaminated connector at the sensor or control unitlikely
Faulty exhaust pressure sensor with an intermittent internal faultlikely
Blocked, sooted or leaking sensor pipe or hose, where the sensor is connected by a pressure linepossible
Exhaust leak near the sensor causing unstable readingspossible
Sensor supply or ground fault caused by a problem elsewhere in the circuitpossible
Fault within the engine control unitrare

How to diagnose

Read all stored and pending codes and the freeze frame data to see engine speed, load and temperature when the fault set, and note any related boost or particulate filter codes.
Check for technical service bulletins or known issues for the specific model and engine.
Inspect the sensor, its wiring and connector for heat damage, chafing, corrosion, water ingress and a secure fit.
With the engine running, view the live exhaust pressure reading and compare it with load and speed; gently wiggle the wiring and connector to see if the signal drops out or jumps.
Check the sensor's supply voltage, ground and signal at the connector against the manufacturer's specification.
Where fitted, inspect the sensor's pressure pipe or hose for blockage, cracking, soot build-up or leaks.
Look for exhaust leaks around the manifold, turbo and the sensor mounting.
Test the wiring for continuity and shorts between the sensor and control unit, and only suspect the control unit once everything else is proven good.

How to fix

Repair or replace damaged wiring and fix any open circuit or high resistance.
Clean, repair or replace a corroded or loose connector and its terminals.
Replace the exhaust pressure sensor if it is confirmed faulty.
Clear or replace a blocked or damaged pressure pipe or hose.
Repair any exhaust leak affecting the sensor reading.
Clear the code after repair and road test to confirm it does not return; the control unit should only be replaced or reprogrammed if diagnosis proves it faulty.

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but it may be in limp mode with reduced power. Get it checked soon, as a persistent fault can affect engine and exhaust system control and may lead to further problems.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.