DPF pressure sensor - negative values

[aturnick54]

Recently had a clogged DPF where soot levels were so high it would not force regen. Ended up having a company come and clean it, which worked and the car is currently functioning as expected. It has regened itself since it was cleaned.

They advised the pressure sensor is on its way out. Before they cleaned it, the pressure sensor was reading 0. After cleaning, it did start reading again, sitting at around 4-7. When the engine was shut off, this reading momentarily dropped to negative numbers before going back to 0. Is this normal or is this the sign of a faulty sensor? I assume that previously it had gotten so clogged that it was reading 0 and thus refused to regen.

I do have a replacement aftermarket sensor to fit, however A I would prefer to keep the original genuine part if it's working as expected, and B the hose clamps are a total pain to get to.

[aturnick54]

LordLoveLength said:

They do fail and give strange readings. That would certainly cause the initial blocked DPF.

Is it possible the company put the pipes back on the wrong way round? One is usually bigger than the other to prevent this, but it can happen.
Also the pipes could also be blocked - you really need to remove them with the engine running to ensure they are free flowing.
Best place to fit the aftermarket sensor is the bin.

They didn't remove the DPF or sensor to clean, simply injected cleaner in and somehow forced a regen.

I assumed if the sensor was dodgy, it would throw up an error code. The only errors I had were for blocked DPF which is now sorted and cleared