Parking sensor problem

[columbiers]

Hi,

Got a problem with my 2005 Alhambra- one of the front parking sensors is not working. I found out which one by listening for the clicks and vag com confirmed it was the middle right. No problem,I thought,and ordered a new sensor. Which also doesn't work when fitted.

I then fitted a known good sensor- still not working. The wiring plug has Earth and postive going to it- nothing at the middle purple wire though which I assume is the signal wire so should show nothing?

So is this likely to be a wiring fault or a problem at the module? Vagcom only shows a sensor fault. There is no obvious break in the wires anywhere.

[Mirez]

Well hello! Yes you are correct, the central wire is the signal return. In my experience the front wiring is fairly resilient, I've not seen any issues with this loom so would suspect you are looking at a module fault

[columbiers]

Hi!
Yes that's what I feared. Even used modules are at Ã,£50 upwards on Ebay -is there any way to test the module?

Vag com just says the mid right sensor is not working so that's no help. Thinking about it if it was wiring I'm sure it wouldn't be just restricted to one thin signal wire- it's certainly got + and earth.

If there's no way to test it I guess I'm left with buying a new module and trying it?

[Mirez]

Yes, you can test it - fairly easy really given that the supply and ground and commoned and you've already confirmed you have both at the plug. If you have a multimeter, put it in resistance or continuity mode (have a look at the reference library ref testing glowplugs if you are new to meters) then you want to measure between that central pin at the sensor and pin 7 of C78 back at the control module.

I've just posted a wiring diagram in this thread, which may be of help.

It is possible for the wire to have broken but fairly unlikely, have you checked that the module itself is dry? If the washer pipe has detached then it can take a soaking leading to issues like this. I've taken a number of faulty modules apart, a handful have been repaired by re-soldering the pins of the connector where the joint has corroded as a result of this. If it is as a result of the water then it just depends how far gone it is!

[columbiers]

Thank you. Tested and wire has continuity.
opened up module, can't see any obvious problems and no dampness around it. So I've bought a new (used) module, hopefully a simple swap will solve it.

[SilverBeast]

Have you tried swapping the sensor from the faulty location with one of the others to see if the problem moves with the sensor or stays in the same location?

[columbiers]

Yes, swapped the sensors around, the fault stays in the same place, middle front right. All sensors work when in any other position.