What P047B means
The exhaust pressure sensor measures the pressure ahead of the turbine or in the manifold (Ford: turbine upstream pressure, Cummins: exhaust manifold pressure, older Ford diesels: EBP).
How the engine computer detects it
The module uses it to calculate EGR flow, to control the variable turbine and engine braking, and to protect against overpressure. No manufacturer document available to us uses sensor B – it would be a second sensor, for example on bank 2 of a twin-turbo engine; the description mirrors sensor A. P047B is the plausibility check of sensor B – with the engine off it should read ambient pressure, in operation it should match the model or sensor A (for sensor A Ford uses 15 kPa (2.2 psi)).
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- EGR and turbo control on a substitute value, possibly reduced power
- Exhaust brake or warm-up flap without function
Common causes
- Sensor drifting or faulty Most likely
- Sensing tube or hose blocked or coked Most likely
- Real high back pressure from a clogged particulate filter or catalyst Possible
- Leaking sensing tube or exhaust leak ahead of the sensor Less likely
How to diagnose P047B
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: exhaust pressure sensor b, sensor wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 7B
- Specific fault
Questions drivers ask
Can I drive with code P047B?
Drive gently and only as far as you need to. The engine computer may limit power to protect the engine, so avoid highways and heavy traffic until it's fixed. If the check engine light starts flashing, pull over.
Will my car pass an emissions inspection with P047B?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P047B clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P047B myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: medium. Start with the cheapest checks before replacing expensive parts.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.