'99 Xantia 2.0 HDi Exclusive accelerator pedal sensors

[Edhertz]

My Lexia diagnoses the following fault: 'Accelerator pedal sensor 2 coherence with accelerator pedal 1
Pedal sensor 1 - 63%
Pedal sensor 2 - 76%
Engine speed 2056 rpm
Injection flow 51mm3/cp'
I cleared the fault light once in Italy, but has come on again with same diagnosis, back in UK. Just wondered if someone has 'been there and done that' so to speak. I understand there is a pot (guess this could be sensor 1) activated by the accelerator pedal but not clear about where the other sensor mentioned is. If fault is intermittent could be fun finding out which one is faulty. As usual thanks for any advice and help in advance.

[RichardW]

Presumably there is the main one under the bonnet, and then the one on the pedal for the suspension. Presumably, if the performance is OK, then it must be the suspension one - somewhat surprised it puts the EML on, but then again it is Citroen Try unplugging the suspension one and see what faults it flags up?

[wheeler]

The throttle position sensor for the HDi engine management system is under the bonnet connected to the pedal by a cable, it is one unit but it has 2 sets of tracks in it so both sensors are actually the one unit, you will see there are 4 wires on it.
The one for the suspension directly on the pedal would likley have no input to the engine management system so probably not throw up any fault codes in the management system.

[RichardW]

Thanks wheeler - I did wonder why the suspension one would throw an EML.... Any idea why there are two sets of tracks in the TPS? Guess it must be shot on the OP's car.

[thorter]

As Wheeler says, the Accelerator sensor has two outputs. The outputs track each other as the pedal is pressed, but one output is always about half the other. The ECU checks the ratio, and a coherence fault means that they do not track within the expected limits. The purpose of this is to detect dangerous faults, for example if there was a short to another wire.

Presumably a small error will cause a fault to be flagged, but a larger error will either shut down the engine or cause very reduced performance.

Fred

[Edhertz]

Thanks for replies folks. Cleared fault light, went approx 70 miles and it came on again. Pleased to say that it does not seem to affect the performance in any way. Will have a closer look when it stops raining.

[Chris570]

as said before its the under bonnet one, its an easy job to replace, i've had to do mine.