no abs light

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

Post Reply
robyoz
Posts: 9
Joined: 10 Aug 2006, 00:19
Location:
My Cars:

no abs light

Post by robyoz »

I have no abs light coming on at all have checked bulb and fuses they are fine any ideas?
User avatar
Mandrake
Posts: 8614
Joined: 10 Apr 2005, 17:23
Location: North Lanarkshire, UK
My Cars:
x 664

Post by Mandrake »

Although I havn't seen the circuit diagram, the ABS light should have some additional circuitry - probably just a pullup resistor.

This is so the light is "failsafe" - the default action of the light is to be on, and the ABS computer shorts it out to turn it off. (Rather than the reverse - providing power to turn it on)

This is done so that unplugging the ABS computer (or the fuse that powers it) causes the light to stay on, rather than stay off.

If possible trace from the bulb and see if you can find any resistors/diodes/transistors/relays connected to it.

Also try unplugging the plug from the ABS computer and turning on the key - if the light now comes on there could be a fault in the ABS computer, if it stays off, the fault is not in the ABS computer, and is probably somewhere in the instrument panel or wiring.

One more thing - does the ABS actually work ? (Does it prevent the wheels locking on a wet road ?)

Regards,
Simon
Simon

1997 Xantia S1 3.0 V6 Auto Exclusive in Silex Grey
2016 Nissan Leaf Tekna 30kWh in White

2011 Peugeot Ion Full Electric in Silver
1977 G Special 1129cc LHD
1978 CX 2400
1997 Xantia S1 2.0i Auto VSX
1998 Xantia S2 3.0 V6 Auto Exclusive
User avatar
CitroJim
A very naughty boy
Posts: 49518
Joined: 30 Apr 2005, 23:33
Location: Paggers
My Cars: Bluebell the AX, Polly the C3 Picasso, Pix the Nissan Pixo, Propel the duathlon bike, TCR Pro the road bike and Fuji the TT bike...
x 6156
Contact:

Post by CitroJim »

I had this on mine.

There is a wiring connector under ABS block and very hard to get to. It has three wires and if this is pulled apart it puts the light out despite the ABS being non-functional. I guess it's a "trick" to try and fool an MOT tester if the ABS is duff. I found my connector to be just half pulled apart and when I reconnected it the ABS lamp came on full-time. One wheel sensor was later found to be dead. I found out all this after pulling the dash apart to check the bulb.

The light is operated from a relay and IIRC it's the pale green one near the ABS ECU. The ECU operates this relay to put the light off. When the ABS ECU goes through it's self test when you first turn on the ignition you can hear this relay clicking and the lamp should flash on an off a few times.
Jim

Runner, cyclist, time triallist, duathlete, Citroen AX fan and the CCC Citroenian 'From A to Z' Columnist...
robyoz
Posts: 9
Joined: 10 Aug 2006, 00:19
Location:
My Cars:

Post by robyoz »

Thanx for replys abs def dont work so sounds like previous owner has done something to get it through mot should of thought of that before taking fiddly dash apart :evil:
Post Reply