ABS problem - what do to next ?

[campervan]

Hi,

Hoping someone could suggest where to go next with my A4 ABS problem.

A few weeks ago I got the orange abs lights and the flashing brake fault light up (complete with 3 beeps when starting the car).

My handheld code reader indicated an ECU fault.

Had my unit tested and it was 'unrepairable' so replaced it with a used unit. This cleared the red warning light/beep.

The orange ABS light would come on after a few minutes driving - before it did the ABS seemed to operate when the brakes were applied even a low speeds.

I re-scanned and got a rear ABS sensor fault.

I removed and cleaned the sensor (it was covered in metal particles - like a magnet and iron filings).

This cleared all the fault code and the orange light but the ABS seems to operate everytime the brakes are applied even at low speeds.

I'm a bit stuck where to go from here and would appreciate any help

Thanks a lot

[HTC]

So you've investigated the wheel sensor and the symptoms have changed. I would replace that particular sensor.

Are you still getting a fault related to the rear sensor?

[aragorn]

Yer the fact the ABS is activating means that the AbS ecu thinks one of the wheels is locked, ie no signal from the sensor. Have you driven the car properly? you usually have to get upto 15-20mph before the ABS ecu will realise there is a fault so if youve just driven it round the street for testing then its likely the fault it still there.

I'd replace that rear sensor.

[dieselfitter251]

Agreed, though if you can, you may want blast the hub with air to get any sebris of the ABS ring, might as well do all four, give it all a good clean up.

You may still have to replace that sensor.

[campervan]

Thanks for the suggestions.

After a good drive I'm now getting the orange ABS light back up.

I've ordered a new sensor and will give things a good clean when I fit it.

Thanks again

[campervan]

Just fitted the new sensor.

No ABS light on dash and no codes appear on my hand held reader.

But....ABS still coming on at low speeds.

Help - where do I go next ?


Thanks in anticipation

[SonicDeathmonkey]

Dude, broadly similar problem to my car. Did you use vagcom to tell which sensor was toast? If so, how?

[campervan]

Havent got VAG-COM (yet)
Been using a hand held OBD code reader. It told me the rear right was gone.

[dieselfitter251]

What car you got? If it's a quattro then there's a hefty price for replacement rear sensors, if it FWD then give Aragorn a bell ...

[aragorn]

me? i dont have any FWD bits...

i think you may be thinking of auoran whos breaking a V6?

[naefeart_A4]

I've just had this problem rectified on my tqs - Audi replaced both rear outer cv joints.

n

[auroan]

me? i dont have any FWD bits...

i think you may be thinking of auoran whos breaking a V6?

Yup it's me.... I've got all four sensors, front/rear hubs, ecu, pump etc etc (abs was fine on the motor before I started breaking).... infact the whole car was fine but is worth more in bits.

[campervan]

Replaced both rear sensors now - still getting ABS on at low speeds.

Would welcome any suggestions

Thanks

[aragorn]

whats the ABS rings like on the disks themselves?

If they're muntered you might need some new ones, although if they've been on there that long that they're knackered, the disks probably arent in very good nick either...

[campervan]

I'll have a look at the disks. They are fairly new - few months old - but worth a look.

I'm rapidly approaching the limits of my knowledege - is it obvious what to check ? Is is easily accesable.

Thanks again

[aragorn]

On a FWD the trigger ring is pressed onto the back of the disk.

Who replaced the disks? they may have used new ABS rings, or they may have just removed the old rings from the old disks and fitted them to the new ones...

To access them, you need to remove the brake calipers and undo the hub bearings, then remove the disk from the car.

[auroan]

Eh ? I thought the ring was in the hub not the disks

[aragorn]

the hub and disk are one and the same on a FWD B5 A4.

Disk has taper bearings inside it and the ABS ring pressed onto the back of it.

[dieselfitter251]

I've got two ABS rings (bought in error a while ago) for the rear if required. Nae use tae me as a've goat a qwattro....
(sorry for the phoenetic scottish, dinnay ken whit came ower mi)...

[aragorn]

Wi dinnae aw spek like that yi ken. :P

[dieselfitter251]

Aye, I know. Not even my accent. I'm from Ayrshire!

[campervan]

I'll have a look at the rings.

Update on problem:

Drove to work this morning - ABS came on at low speed as before. After a few miles it stopped coming on and no warning light i.e. all seemed OK. However, I then noticed a rapid ticking from the general direction of the ABS pump/controller. Does this give any more clues ?

Thanks

[dieselfitter251]

Lost on me. Sorry. Conjecture would be that there's a problem with one or some of the solenoids in the pump / module. But that is just a guess.

[campervan]

After living with this for months I've had enough and need to resurect the fault finding.

Sensor rings have checked out OK.

Worth changing the pump module itself ? Is this a big job ?

Any other testing I can do before swapping the pump ?

Thanks in anticipation

[ian52]

what about sending the module away to one of the places that repair them and getting it checked out?

[aragorn]

is it just triggering the ABS, or is it bringing up the large warning light etc?

If its bringing up the large warning what faults are the ABS unit recording?

[aragorn]

is it just triggering the ABS, or is it bringing up the large warning light etc?

If its bringing up the large warning what faults are the ABS unit recording?

[aragorn]

is it just triggering the ABS, or is it bringing up the large warning light etc?

If its bringing up the large warning what faults are the ABS unit recording?

[dieselfitter251]

DO you know anybody with vagcom or have access to yourself? A good indipendant garage might help, save money over a steelership too. It may give more clues than the hand held unit...hand held unit.... ffffnar!

sorry, couldn't resist.

[Blue_Thunder]

If you know someone local with a similar aged B5, you could swap your ABS ECU's to see if that solves the problem. Would be a 10 minute job.

[dieselfitter251]

Good point. Where are you campervan. Most folks on here will be willing to muck in if you're close enough, all they may require is a luke warm bacon butty and a luke warm ale..... Anywhere near East Lothian ;O) ??

[campervan]

Thanks again for the help.

I've goy myself VAG com and it is showing intermitant faults on the two rear sensors (i.e the new ones that I fitted !)

VAG COM indicates all the wheels are reading the same speed.

Tried to do an output test but am getting a few problems:
- either "no response from controller" or
- says tests complete but nothing appears to have happened or
- nothing seems to happen at all !

I'm new to VAG COM - am I missing something ?

Also - I cant access any groups in Basic Settings, I get "group not available message" on any group.


I've replaced the ECU but it could be faulty so will look for another similar car to do the swop

Cheers

[aragorn]

Intermittant faults on sensors you have replaced could indicate that the reluctor on the back of the brake disk (FWD) or on the CV joint (Quattro) is worn/contaminated/rusty...

Might be worth taking a look at them.

[NL_B5S4]

Has there been any progress on this problem? I've the same issue and feel it may be the ABS ECU acting up.

[campervan]

the story continues here...

http://www.audi-sport.net/vb/showthr...395#post721395