ABS light on constantly

paulbx · Post by **paulbx** » 20 Sep 2010, 16:09

Hi folks

Xantia estate HDi 90 SX.

Its no surprise its been flashing on/off and going away for months on end for 2 years now (always good for MOT oddly!!).

I don't have a Lexia so any advice gratefully accepted.

One - find the dodgy wheel and Two - how to fix - I know its a pain if its a front one that's gone.

I've hard could be dirt or poor connection if I am lucky!

many thanks in advance

Paul

Xaccers · Post by **Xaccers** » 20 Sep 2010, 17:02

If you do a search there's several threads on it, which detail which pins you need to check on the ABS ECU connector to determine which sensor is misbehaving.
You'll need the Mk2 pin layout.
The fronts are a doddle to replace, the rears are a bit more of a pain.

paulbx · Post by **paulbx** » 20 Sep 2010, 17:14

Thanks for that I'll try those keywords

Xaccers · Post by **Xaccers** » 20 Sep 2010, 17:20

Here you go, it's in the handy hints and tips section:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=26012

Old-Guy · Post by **Old-Guy** » 20 Sep 2010, 18:05

My money's on a grotty connection at the ECU plug.

Garages and dealers love to plug in a Lexia (or equivalent) which always diagnoses a faulty sensor (£120+ plus labour) - that's what the light's telling you anyway.

So first they replace the 'faulty' sensor - without curing the fault - THEN they do what they should have done in the first place and look for a bad connection.

Of course the bill would then have been so much smaller!

paulbx · Post by **paulbx** » 21 Sep 2010, 16:26

Cheers old guy - I'll try there at weekend.

I've tried to search previous posts on measuring current on ECU to find which wheel is at fault but no luck on searching.

many thanks

Paul

Xaccers · Post by **Xaccers** » 21 Sep 2010, 17:17

You want to measure resistance not current, and on the plug that goes to the abs ecu by the lhm tank not the ecu itself.

paulbx · Post by **paulbx** » 22 Sep 2010, 13:38

Xac cheers for that will do this weekend.

Paul

paulbx · Post by **paulbx** » 03 Oct 2010, 10:27

Hi folks

Right plug off, engine on, resistance on meter on, only got a reading across one pair . I don't think I am doing this right as the only resistance I got was across one diagonal pair.

Does anyone have a diagram that actually shows the plug and the wiring pin outs/ The PDFs I've found do NOT show the plug only the ABS warning light.

I can't believe they are all screwed bar one!

any help gratefully received

Paul

addo · Post by **addo** » 03 Oct 2010, 10:35

Yes, follow the link posted above and there is a very clear photo.

paulbx · Post by **paulbx** » 03 Oct 2010, 11:14

Ooops I can see clearly now -cheers!

Old-Guy · Post by **Old-Guy** » 03 Oct 2010, 12:50

As a clincher before buying a new sensor: with the 'ignition' off, unplug the sensor and test for a small AC voltage with a Digital Multi-Meter while someone spins the relevant wheel. You'll probably need 'test' the other good side first to know what to expect.

The DMM needs to be set on AC volts to give a reading because the sensor produces a string of pulses.

paulbx · Post by **paulbx** » 03 Oct 2010, 14:40

Many thanks - with that diagram - I found it!

--Next silly question - the graphic says front left for example (that is the one with zero reading) is that offside or nearside

Near-side of the car being the Passenger's side and the Off-side is the Driver's side. Sorry but just want to sure - assume the diagram means "left side" from as you view it from front of car?

Thanks again for all the great help from this forum!

Paul

Old-Guy · Post by **Old-Guy** » 03 Oct 2010, 14:52

I've used this diagram in the past and I'm sure I would have remembered if Left had not meant Nearside.

As you've got a zero reading at the ECU connection I'd check the connector on the strut - I'm fairly sure there's no intermediate connection on the front sensors - and that the sensor's wires aren't broken. Intermittent then permanent doesn't sound like an electronic failure (they usually fail totally) more like an iffy connection (though it might be internal to the sensor.

paulbx · Post by **paulbx** » 03 Oct 2010, 14:54

Thanks Old Guy - so there' s a connector on the strut - I'll go look for that!

cheers

paul

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