High DPF Pressure with engine off??

[Joe H]

I did some work around the DPF including disconnecting the pipes leading to the pressure sensor.
The Pressure Sensor is now showing around 65,531 hPa (should be more like 67), with the last digit changing when revved.

I assumed I had connected something up wrong but then noticed it was reading that with the engine off (ignition on). I didnt have time to look at it any more.

Is that pointing to a faulty Pressure Sensor? Seems unlikely as I didnt touch it or the wiring.
Or does VIDA display the last reading with engine running?

Cheers
Joe

[outnumbered]

Hi Joe have yopu the pipes the right way on the sensor there is a large hole and a smaller hole.
Mike

[poiuytre111]

Im not familiar with volvo dpf pressure sensors but surely they all have to show normal atmospheric pressure when the engine stops - unless faulty. After I had a bmw dpf done, we looked at the reported values to show it was fixed but one was some way off when engine stopped so we changed it.

[Joe H]

Originally Posted by outnumbered

Hi Joe have yopu the pipes the right way on the sensor there is a large hole and a smaller hole.
Mike

Mike - I assumed I had done something like that until I saw it was reporting the same value with engine off, when it shouldnt matter how the pipes were connected.
Joe

[Joe H]

Originally Posted by poiuytre111

Im not familiar with volvo dpf pressure sensors but surely they all have to show normal atmospheric pressure when the engine stops - unless faulty..

I borrowed a working one and oddly it showed the same high value when connected then showed normal ones.
Plugged the original in (with no pipes connected) and it still shows the wrong value.

Not sure what is going on. Pipes didnt seem to be blocked, wiring seems fine (wiggling it doesnt make any difference) so it seems the sensor just went bad. Stange coincidence !

Thanks for the comments though guys
Joe

[poiuytre111]

In your situation I would take some wires from the sensor direct to (I presume) the ecu just to check you haven't got a problem in the loom or at a connector somewhere.

[Joe H]

Originally Posted by poiuytre111

In your situation I would take some wires from the sensor direct to (I presume) the ecu just to check you haven't got a problem in the loom or at a connector somewhere.

I gave all the wirres and connectors a good tug and wiggle to see if anything changed so in this case I will leave it and see if the problem comes back.

But in practice how do I do something like that? I dont like the idea of cutting and resoldering wires as it is likely to cause problems which didnt exist before, and it doesnt rule out connector issues but that is the only way I can think to do it.
Thanks
Joe

[poiuytre111]

Well, if I were doing it I would find out where the wires go, which I presume to be some pins on the ECU so a wiring diagram is essential - by all means check the wiring colours to confirm. I would unplug the ecu to check the pins and connector sockets look clean and maybe spray with servisol contact cleaner. You may find the metal pins are exposed on the back of the ecu connector in which case I would try to solder wire to that point - otherwise I would carefully trim insulation back from the relevant wires (without cutting the copper !) and extend the wires to the sensor . Again, speaking personally I would tack the wires direct to the sensor on a temporary basis maybe with croc clips. A different approach would be to check continuity between the ecu contacts and the pressure sensor plug (attached to loom, not the sensor itself).