abs faults

[sleeper16 0]

hi i have an issue with my abs light is on all the time and once or twice the light will go off and the brakes come on on there own or when pedal is pressed come on very harshly almost locking up only ever at slower speeds.

 

i have tried vag com and nothing came up.

 

any thoughts on what this could be? or how to resolve?

 

cheers

[mr.ots 10]

If the ABS light came on then the fault should have been stored on the ECU. Is Vagcom communicating with the ABS ECU?

[Supercharged 2]

Check the ABS ecu for water damage...

[sleeper16 0]

Chhers for replies I think it is connecting to abs ecu will double check. Where is the abs ecu located?

 

Cheers

[Supercharged 2]

It's inside the passenger kicck panel near the door - 2 screws

 

Check this for any signs of water - green corrosion

[sleeper16 0]

ok had a look at ecu all the terminals were fine nice n shiney. but i think i may have sorted it. the plug for the harness has a metal clip lock mechanism on it and this was half open. started the car light goes off as it should now so will give it a drive later to give the brakes a test.

 

 

cheers for all the help fellas!

[sleeper16 0]

Ok been for a good drive bout 40 mile its not fixed it so will try vag com again now the ecu is plugged in properly

[Supercharged 2]

Yep, if the light comes on then a code should be logged - ABS codes never clear themselves like engine DTC's

[craigowl 0]

My ABS light stays on when I start car for first time. If I drive somewhere, or stop engine and restart for 2nd time light goes off as normal.

Replaced sensors a few months ago in attempt to correct, but after a while of being OK fault has reappeared.

Can live with this, obviously, and car passed MOT like this, but wondered if anyone had answer to problem.

[sleeper16 0]

hi guys sorry its been a while had a lot on. vag com shows no codes. im thinking it must be a peed ring or sensor as it only comes on when the car moves. i had a run down the motorway with actual working abs the other day too and the brakes were rather decent! will check rotors today and test sensors. anything else to look out for?

 

cheers

[RW1 0]

Sensors & rotors should throw faults, so will be surprised if anything is found. I suspect the ABS unit itself is misbehaving. Particularly if the ABS is working.

 

I would also check the wires. The lamp is illuminated by the ABS unit by the earth side being made. Follow as best you can the yellow with red stripe wire back from the dash lamp unit to the ABS unit. It goes to the fuse box initially on plug X. Comes out on plug W as a grey with black stripe and goe to the onto a in line joint in the ABS loom to the ABS controller. The joining is onto another grey with black stripe which is on pin 52 on the ABS controller connector. This wire also goes to one of the ABS relays up behind the glove box.

 

If any part of the wiring has rubbed and is grounded, it will bring on the ABS dash warning lamp.

 

Fuse box connector W is a 6 pin Green plug, X is a 8 pin green connector. Top corner of the fuse relay plate near the bonnet pull handle.

 

.

Edited March 19, 2011 by RW1

[sleeper16 0]

ok so no faults on abs module but went round and checked the restance of the sensors(was suspecting either a sensor or a speedring to broke loose from the disc) and found one of the rear sensors had gone so replaced with a spare i had and works a treat. not sure why it hasnt logged it on ecu though!

 

---------- Post added at 10:14 PM ---------- Previous post was at 10:13 PM ----------

 

cheers rw1 a comprehensive explanation! think its all fixed for now will see how it goes over a few days might be worth checking the datalines and cables anyway.