Blocked, sooty or leaking exhaust pressure sensor pipe or hose; Faulty exhaust pressure sensor (drifted or stuck signal); Damaged wiring, poor connector contact or corrosion in the sensor circuit; Exhaust leak near the sensor or upstream of it affecting the pressure reading; Restricted exhaust, such as a blocked particulate filter or catalyst, or a turbo fault altering pressure; Fault in the sensor supply or reference voltage shared with other sensors; Control unit fault or outdated software, where a manufacturer bulletin confirms it.

P047B

Exhaust Pressure Sensor B Circuit Range/Performance.

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
7B: FaultThe specific fault in that area

What it means

P047B is the generic code for an exhaust pressure sensor B circuit range or performance fault. The engine control unit has compared the signal from this sensor with what it expects, or with other sensors such as ambient or intake pressure, and found it implausible, stuck, slow to respond or offset. Which position 'sensor B' refers to (bank, location or pre/post turbo or filter) depends on the engine, so check the vehicle-specific information.

Symptoms

Engine management light on
Reduced power or limp mode
Poor or erratic turbo boost response
Increased smoke or rough running under load
Failed or repeated particulate filter regeneration
Poor fuel economy

Possible causes

Blocked, sooty or leaking exhaust pressure sensor pipe or hoselikely
Faulty exhaust pressure sensor (drifted or stuck signal)likely
Damaged wiring, poor connector contact or corrosion in the sensor circuitlikely
Exhaust leak near the sensor or upstream of it affecting the pressure readingpossible
Restricted exhaust, such as a blocked particulate filter or catalyst, or a turbo fault altering pressurepossible
Fault in the sensor supply or reference voltage shared with other sensorsrare
Control unit fault or outdated software, where a manufacturer bulletin confirms itrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting engine load, speed and temperature when the fault set
Look for other codes on turbo, boost, particulate filter or reference voltage circuits, and deal with those first
Inspect the sensor, its wiring and connector for damage, heat damage, water ingress and corrosion
Check the pressure sensing pipe or hose, where fitted, for blockage, cracks, splits and loose connections
Inspect the exhaust for leaks around joints, gaskets and the sensor port
With the engine off, compare the live exhaust pressure reading with ambient pressure; it should read close to atmospheric
Check live data while revving the engine and see if the reading responds smoothly and in line with load
Check the sensor supply voltage, signal and ground with a multimeter against the manufacturer's specification, and test for exhaust restriction if readings suggest it

How to fix

Clear or replace a blocked or damaged sensing pipe or hose
Replace the exhaust pressure sensor if it is faulty or reads out of range
Repair damaged wiring or clean and restore poor connector contacts
Repair exhaust leaks and renew faulty gaskets
Address any exhaust restriction or turbo fault found, following the manufacturer's procedure
Apply a software update only where an outdated calibration is a documented cause for that vehicle

Can I keep driving?

Medium severity

Short, gentle drives are usually possible, but limp mode or a restricted exhaust can hurt the engine or filter, so get it checked soon. Stop driving if power drops sharply, there is heavy smoke or warning lights flash.

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