P245F: Particulate Filter Pressure Sensor B Circuit Range/Performance
What to do
Ask for the sensor's pressure pipes to be checked and cleared before the sensor is replaced. They block with soot, that is the commonest cause of this code, and clearing them costs almost nothing next to a new sensor.
Mention whether the car has been running regenerations more often than usual — a cooling fan running on after parking, or a hot smell — since that is the symptom this fault produces before anything else becomes obvious.
Do not leave it indefinitely. While this sensor is misreading, the system cannot tell how full the particulate filter is, and the failure that follows is a blocked filter, which is a far larger bill.
What this code means
The second particulate filter pressure sensor is producing a reading that is electrically valid but not credible.
Some systems measure filter loading with two absolute pressure sensors rather than one differential sensor — one before the filter and one after — and compute the difference themselves. Sensor B is the second of that pair, and this code says its output does not agree with what the rest of the system implies it should be.
The signal is in range, which is what makes this harder than a circuit fault. There is no open, no short, and nothing obviously broken; the number is simply wrong. The classic evidence is a sensor that reads a plausible pressure with the engine stopped, when it should be reading atmospheric like everything else.
Soot in the sensor's take-off pipe is the usual cause. These pipes are narrow, they run hot, and they slowly fill — and a partially blocked pipe damps the reading rather than killing it, which is exactly how a sensor ends up plausible and wrong.
Blow the pipes through before condemning the sensor. It is a five-minute check that resolves a large share of these.
The consequence is that the module cannot judge filter loading correctly. It may command regenerations that are not needed, or fail to command one that is — and the second of those quietly blocks the filter.
Likely causes
Start here
Less common
- High resistance in sensor wiring · moderate
- Exhaust leak upstream of the sensor · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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