ABS problem, ECU pinout info wanted for Mk4 Teves?

[kenhall1202]

My 2.1TD (RP no 7249) has an ABS problem (warning light on and 'ABS OUT OF USE' message).

A Lexia session indicated stored faults with the right rear wheel speed signal. The faults can be cleared but immediately re-appear again after a short drive. A mobile Lexia run shows a matching correct but intermittent speed signal from the right rear sensor.

Fitting a new sensor has made no improvement (old one seemed fine with a 1080 ohm resistance measured and plug contacts were clean).

I now suspect a wiring problem between the sensor and the ABS ECU so will need to do a resistance check backwards from the ECU multiplug.

Please can anyone confirm the pinouts for resistance checking. The unconfirmed information I have for the Mk 4 Teves is as follows:

Front left - pins 15 and 30
Front right - pins 1 and 6
Rear left - pins 19 and 28
Rear right - pins 29 and 31

Thanks

Ken

[Peter.N.]

Hi Ken

All my figures check out except the first one, I have 15 and 13 but I suspect that I have written it down wrong.

I would suggest that you short the wires together at one end and measure the resistance at the other, you should have a very low reading, probably not much more than 1 ohm, if you have much more or the reading fluctuates you have a wiring problem.

Peter

[xmexclusive]

Hi Ken

Pin numbers are correct but I think you have the front sides transposed.
My source is RTA CIP701.3 Aug 2000 & Jly 1998 editions, p130 & p136.
Sensor 155 - pins 15/30 - avant droite.
Sensor 156 - pins 1/6 - avant gauche.
Sensor 157 - pins 28/19 - arriere gauche.
Sensor 158 - pins 29/31 - arriere droite.

John

This post has been edited by xmexclusive on November 05, 2012 11:57 pm

[kenhall1202]

Hi Peter and John,

Thanks for the quick responses.

I think the reason for me transposing the fronts is because I was looking at the small pictorial sensor positions on the page 130 circuit diagram which don't tie up with the item number descriptions for 155 and 156 on page 136.

Anyway, once I gain access to the ECU all four pairs will all be checked out.

Ken

This post has been edited by kenhall1202 on November 14, 2012 07:58 pm

[techmanagain]

As a non-electrical reader, can I suggest thet you check the wiring connector as it goes over the rear axle? Diffucult to get and certainly the wrong place to have a push-in connector but it is a source of common problem on XMs, I understand.

[kenhall1202]

QUOTE (techmanagain @ November 05, 2012 04:08 pm) 

As a non-electrical reader, can I suggest thet you check the wiring connector as it goes over the rear axle?  Diffucult to get and certainly the wrong place to have a push-in connector but it is a source of common problem on XMs, I understand.

Hi techmanagain,

I did check this awkwardly located plug/socket when I renewed the sensor and as far as I could tell it was clean and corrosion free.

This morning the ABS fault wasn't there but reappeared again after a few miles test drive so there is obviously an intermittent connection somewhere.

Resistance checks at the (clean and dry) ABS ECU plug connectors gave the following results:

Pins 15+30 1080 ohms
Pins 1+6 1060 ohms
Pins 19+28 1035 ohms
Pins 29+31 Infinite resistance

Job for tomorrow (weather permitting!) get underneath and check the rear ABS cable run for physical damage. I'm wondering if I might have damaged the cable across the back axle tube, through dropping and raising the subframe, when I replaced a corroded section of 4.5mm pipe??

Ken

[kenhall1202]

Fixed!!

One of the previous owner's sins had come back to haunt me.

When I bought the car nearly 12 years ago from a Citroen dealer they failed to properly fix a recurrent ABS fault which started appearing soon after purchase. I eventually found that both of the rear sensor twisted pair cables running along the offside sill inner face had been cut or snapped at some time. The repair by persons unknown had consisted of twisting the bare wire ends together with the addition of a token wrap of PVC tape. The eventual corrosion and high resistance of these makeshift connections was causing the ABS problem.

I made a repair by soldering and shrink sleeving the wires but found it difficult because there was no spare slack in the cables to play with and the copper strands were coated with black oxide as if the cable had been overheated. This oxide was very difficult to fully clean off and I had to resort to using plumbing flux to get the solder to wet the joints.

Anyhow 12 years later one of my solder joints gave up the ghost to put the ABS out of action again. The repair has consisted of splicing in two new sections of twisted pair cable. If this repair lasts another 12 years then I will be happy!!

Ken