Faulty exhaust pressure sensor B; Blocked, sooted or damaged pressure sensor pipe or port (where a remote sensor is fitted); Damaged, chafed or corroded wiring to the sensor, including short or open circuit; Poor connection at the sensor or control unit connector, with corrosion or water ingress; Exhaust leak near the sensor affecting the reading or the sensor's environment; Fault in the sensor supply or reference voltage or earth; Fault in the engine control unit.

P047A

Exhaust Pressure Sensor B Circuit.

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
7A: FaultThe specific fault in that area

What it means

P047A is the generic code for a fault in the Exhaust Pressure Sensor B circuit. The engine control unit monitors the signal from this sensor and has seen a voltage or signal that is outside the expected range or does not make sense. Which physical sensor is 'B' (for example a post-turbo or second-bank sensor) depends on the vehicle and engine, so check the manufacturer's information for the exact location.

Symptoms

Engine management light on
Reduced power or the engine going into limp mode
Poor or erratic turbo boost control
Increased fuel consumption
Black smoke or rough running under load
Particulate filter regeneration problems on some diesels

Possible causes

Faulty exhaust pressure sensor Blikely
Blocked, sooted or damaged pressure sensor pipe or port (where a remote sensor is fitted)likely
Damaged, chafed or corroded wiring to the sensor, including short or open circuitlikely
Poor connection at the sensor or control unit connector, with corrosion or water ingresspossible
Exhaust leak near the sensor affecting the reading or the sensor's environmentpossible
Fault in the sensor supply or reference voltage or earthpossible
Fault in the engine control unitrare

How to diagnose

Read all stored and pending codes and record the freeze frame data, noting load, speed and temperature when the fault set.
Look for other related codes, such as those for other exhaust pressure sensors, boost pressure or particulate filter, as these point to a shared cause.
Check the sensor, its connector and the wiring for heat damage, chafing, corrosion, water ingress and loose pins.
Inspect the exhaust around the sensor and any sensor pipe for leaks, blockages, soot build-up or damage.
With a scan tool, compare the live exhaust pressure B reading with the other pressure sensors at key on engine off, idle and under load, checking it is plausible.
Check the sensor supply voltage, reference and earth against the manufacturer's wiring diagram, then test signal wire continuity and for shorts to earth or supply.
Test the sensor against the manufacturer's specification if a procedure is available, and only suspect the control unit once wiring and the sensor are proven good.

How to fix

Repair or replace damaged wiring and clean or replace corroded or loose connector terminals.
Clear a blocked sensor pipe or port, or replace it if it is damaged or perished.
Replace the exhaust pressure sensor B if it is faulty, using the correct part for the engine.
Repair any exhaust leaks found near the sensor.
Repair the supply or earth fault if the sensor feed is incorrect.
After repairs, clear the codes and road test to confirm the fault does not return.

Can I keep driving?

Medium severity

The car can usually be driven short distances, but power may be limited and the fault may affect boost control or filter regeneration. Get it checked soon, and stop if the engine loses power severely, smokes heavily or runs roughly.

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