Spot the ABS relay!

Posted: Sat May 24, 2008 7:44 pm

My ABS warning light (Audi 80 1.6 1994) comes on during the mini check when starting the car, goes off for second then comes back on and stays on. From doing a forum search and looking at this tutorial (http://20v.org/brakprob.htm#abs) it seems it could be a problem with the ABS relay. It should be under the dash so I took off the tray under the steering wheel but can't see a relay with a fuse on it. Any pointers to where it is, where else to look? Thanks for any help you can give,
Ben Smile

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Posted: Sat May 24, 2008 8:02 pm

Under the cover on the ABS unit itself, located under the bonnet Wink

Posted: Sat May 24, 2008 8:17 pm

Thanks

Just had a quick look and I will need to buy a torx screwdriver to get the black plastic cover off. Am I right that if the fuse on this relay is blown then I will need to get a new relay? any idea of the cost where best to get one?

Site Moderator Joined: Jan 31, 2003 Posts: 9144

A 1994 car does not have the same system - there is no relay with the fuse on top.

Newbie Joined: Feb 17, 2008 Posts: 17

Thanks

Just had a quick look and I will need to buy a torx screwdriver to get the black plastic cover off. Am I right that if the fuse on this relay is blown then I will need to get a new relay? any idea of the cost where best to get one?

Posted: Mon May 26, 2008 10:21 am

Thanks

Just had a quick look and I will need to buy a torx screwdriver to get the black plastic cover off. Am I right that if the fuse on this relay is blown then I will need to get a new relay? any idea of the cost where best to get one?

Posted: Mon May 26, 2008 10:38 am

Could be an open circuit on a wheel sensor.
Si.

Posted: Mon May 26, 2008 10:46 am

Thanks, I will try to check them too then. Any tips on how to get them/test them? thanks,
ben Smile

Posted: Mon May 26, 2008 1:00 pm

Ninenails has hit the nail on the head Embarassed

wheel sensors everytime and they cost a packet Sad

My advice is to disable it, rip it out and bin it, more trouble than they are worth Twisted Evil

If you want relays then PM me i have plenty and they are all working because they never break in my experience Wink

Posted: Mon May 26, 2008 6:04 pm

Thanks nogin, I'll try and check them this week and I might take you up on the offer if it comes to that Smile

Site Moderator Joined: Jan 31, 2003 Posts: 9144

Very much doubt it is a wheel sensor.

Wheel sensors only start to work when the vehicle moves. In this case the ABS light is on before the car has moved.

The modulator does a self test when first started. There are 2 relays inside the modulator which will trigger the light if they fail.

Posted: Sat Mar 30, 2019 11:32 am

Gents, I'm suffering a similar issue: the ABS warning lights comes on at ignition - and stays on. I've had an auto electrician look at it but says he can't get the abs to 'talk' to his diagnostic laptop unit. My car is a 1994 Tdi Avant. I read elsewhere that 1994 was a 'watershed' year: pre 1994, the ABS couldn't be interrogated, 1994-on, it could. I've taken the cover off the modulator and noted the two relays within, so I guess those are the items Mikes2 refers to here(?) Elsewhere, I read about one behind the dash, incorporating a 10amp fuse: I'll look at that forthwith - mindful of Mike2's advice that these don't feature on 1994 models, yet conscious mine may be a 'crossover' car (not the first time this has happened to me!).

So: any advice you might have would be gratefully received. Also, suggestions for reliable sources for parts: the garage is talking about four new sensors, replacing the ECU and / or ABS control unit. All of which sounds pricey...!

Site Moderator Joined: Jan 31, 2003 Posts: 9144

Find another garage. They don't know what's wrong and want you to pay for their guesswork.

There is unlikely anything wrong with the sensors if the light isn't going off after first coming on.

The changeover was 1993.

ecu is under the rear seat - what's the number from that ?

There is a fuse in the main fusebox for abs and a few other circuits.

Does the abs pump run it's self test ?

Posted: Mon Apr 08, 2019 8:46 pm

Thank you so much for taking the time and trouble to reply. Below some responses to your comments and questions

Find another garage. They don't know what's wrong and want you to pay for their guesswork.

Yup, the electrician certainly doesn't seem to have any answers - but he does at least admit that (cold comfort when you must foot the bill)

There is unlikely anything wrong with the sensors if the light isn't going off after first coming on.

Oddly enough, I thought this also - although my own suspicions were based on the observation that the light goes on - and remains so - yet the wheels haven't turned... so the sensors can't have taken a reading(?)

The changeover was 1993.

Oh! ok. So my car wasn't manufactured during any nebulous 'crossover' period then. Good to know.

ECU is under the rear seat - what's the number from that?
Under the rear seat? Oh. I read somewhere that with an Avant, it's located near the wheel arch. I've certainly seen something which resembles an ECU there. I don't currently have the car to hand, but once it's back, I'll have a good poke around again - and confirm the part number.

There is a fuse in the main fusebox for abs and a few other circuits.

Jesus, I'd hope the electrician had thought to check the fuses - please God, tell me he did! At some point down the years, the sticker peeled off the fusebox cover so I had to refer to online pics - but then failed to see the listing for fuse 31: ABS. I'll check that asap. I've also heard tell of an ABS relay with integral fuse located under the rear passenger seat...?

Does the abs pump run it's self test?

I believe this is audible(?) I haven't heard anything