Xantia 2.1TD Grey Sensor On Engine Block

[bddeazeley]

Hi Folks,
Just a query about the grey sensor that is located on the front of the engine block on my 2.1TD Xantia (XUD11 bte) which I believe is an oil pressure sensor or switch. The plug to this sensor was accidentally disconnected some time ago and I only noticed it the other day. The strange thing is the oil pressure warning light operated as normal, ie the light went off when the engine was started, whilst the plug was disconnected. After reconnecting the grey plug to the sensor the car now feels far more responsive than it was before and the engine which had a slight diesel knock lasting a couple of seconds mostly when decelerating or changing gear no longer has the knock. Have I got it wrong or is this grey sensor more than an oil pressure switch?

[Chris570]

i would imagine its a knock sensor

[robert_e_smart]

If it has one wire going into it, its an oil pressure switch, though I don't know if the oil pressure switch would account for the improvements you note. Not impossible that it plays a part on Lucas Epic.

[CitroJim]

i would imagine its a knock sensor

Diesels don't have knock sensors.

Yep, if the sensor is on the front of the block in the vicinity of the oil filter then it's the pressure sender.

I can't possibly think how it would affect running. If it was connected to the engine ECU you'd have thought it would have stopped the engine on low oil pressure, not made it run badly!!!

Mind you, with it disconnected the oil light should not have worked at all. That is odd...

[bddeazeley]

Thanks for the quick replies. Yes the sensor only has 1 wire and yes it is in the vicinity of the oil filter so I guess it is an oil pressure switch. The oil pressure warning light has never faulted and I would have expected it to have remained on whilst the lead was disconnected. One other symptom that I did not mention was if the car was driven above 3500 rpm there was a loss of power in a rhythmic manner every second ie loss of power for one second then ok for the next second and that would continue as long as the car was above 3500 rpm. That symptom has also cleared up and the car will now go up to approx 5200 rpm then the govenor kicks in to limit the engine. All very confusing.

[steelcityuk]

Not sure about Xantias but could it be a needle lift sensor? Only applies to Lucas injection whereas my XM has Bosch so I'm not certain.

Steve.

[spider]

Oil level sensor maybe ?

Although I think those are fitted to the back and in the sump not the block. The one near the oil filter is the pressure switch, it has to be near the filter really anyway.

[wheeler]

i would imagine its a knock sensor

Diesels don't have knock sensors.

They do now... The 1.4 & 1.6 HDi's have knock sensors. Lexia calls it the accelerometer though.

[CitroJim]

i would imagine its a knock sensor

Diesels don't have knock sensors.

They do now... The 1.4 & 1.6 HDi's have knock sensors. Lexia calls it the accelerometer though.

Thanks Wheeler How bloody amazing! Don't quite see how it can be called an accelerometer though. Is it like a petrol one and basically a microphone listening for knock?

[wheeler]

Works & looks just the same, piezo crystal typ that produce a very small voltage when it is vibrated.
I think accelerometer is just a bad translation from French.