ABS Warning light (not ECU - i think!)

[Joni_s]

My ABS warning light (i.e. the little yellow light) and the Large red exclamation came on yesterday at startup. The night had not been particularly cold but it had been fairly windy and wet i think.

I think it seems strange that the lights came on while the car was stationary.

These lights have been on before but this was about 3 months ago when the ECU failed. I did the DIY solder fix which has been fine ever since and havent seen any lights since then. I would have thought if my soldering had failed then it would be likely that the lights would come on while driving the car e.g. after going over a big bump and the wire disconnecting. So i think i can possibly rule this out.

Also i found that when you have a wheel sensor problem it tends to show up on teh dash only when you move away from stationary but my lights came on just when i turned hte key - before i had driven away.

I took it to hte local garage as i'm driving a long distance this weekend so thought i should check it out. They have diagnostics but said they couldnt get it to work with my car as they htink its too old (98 s reg a4 2.5 tdi quattro). This may be true but if it isnt then it also may indicate that the ecu is not communicating due to my soldering job failing? Although i forgot to ask if they were able ot communicate with other systems in the car.

The garage tested the voltage of all wheel sensors and found one was lower than the other 3 but because i hadnt driven before the lights came on i am sceptical as to whether this is the problem and don't want to lay out cash for a problem that doesnt exist!

I read somewhere on hte forum that the level sensors can go on a4s - i assume htis means the brake fluid level sensors?

Any suggestions or ways of finding out hte problem would be gratefully received!

 

[mwarrey]

Hi, I had this problem on my S4 back last summer. It turned out to be the abs ecu which I sent away for repair. With a problem like this you really have to use VAG-Com (or similar) to scan the relevant controllers for fault codes.

 

[Joni_s]

i doubt it is the ecu based on what i said above but it still could be. I can get the car hooked up to vag com for £40 byt hte local specialist or i could get a new wheel sensor for £37.50 plus VAT from GSF. decisions decisions. I reckon fitting the wheel sensor to my car to see if that is the problem will mean that i can't take it back to GSF if the problem lies elsewhere so may just have to take it in for a hook up!

 

[mas]

getting wheel sensors out can be a right pita.
£37 sounds very cheap though.

Vag com would at least tell you if there is any communication to the ecu - try a post asking - there must be someone near you that would hook up for a beer rather than £40. If it is a sensor vagcom should tell you which one. A faulty sensor could be picked up before you move, I think it checks the resistance as part of the start up.

The lights on the dashboard do come on if there is no communication with the ecu.

the car isnt too old - although it may be that the local garage dont have the right kit - vag com reads earlier tcars than yours.

I think that the lights on just means that the abs is disabled. I drove around for a couple of weeks with the lights on and fuse out when I had a crack in the reluctor ring on one of the front cv joints. The car behaved fine - just no abs.