Constant beeping, red brake light and abs!!!!

D

datsundrew

A2OC Donor
I’ll try and keep it brief, but a lot has happened! 1.4tdi, AMF, ‘01
i have had is for a couple of months now with the red brake warning light and 3 beeps that occurs after around 7 mile/ 20 minutes driving. There is never a code logged and once the beeping started with the car parked and engine running. The brake switch is recent, and brake lights work etc. Looking at VCDS shows brake pressure goes from 0-upwards with pressure on the pedal.
so today I had a session on the front brakes, armed with new callipers , back plates and abs sensors as I’ve read this could cause an issue. Whilst apart I gave the housings a good clean up and paint, the old sensors were rusted in solid and I had to resort to carefully drilling them out. I got it all back together, brakes bled and took it out for a drive, laptop ready on the passenger seat plugged in to the OBD. Immediately I got moving the abs light came on, and after about a mile checked for codes…..nothing. Switch off and re start, and pull away and this time I got the red brake warning light, abs light and this time it beeps constantly, not 3 beeps but about 500 beeps until I pulled over! Again, no codes.
i re start and again constant beeps and lights. I pull over again, switch off, open the bonnet and check brake fluid level, fine, bonnet on, start and drive off, but this time no lights, no beeps, and the brakes better than ever. WHAT THE HELL IS GOING ON HERE???
As yet, Ive not driven it it’s 7miles/ 20 mins to get the usual light and beeps and yellow triangle, but I suspect it’ll be the same.
Any pointers or suggestions would be massively appreciated!
 

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Yaw and pitch sensors? Two separate items on earlier cars and combined on later ones. Are you running all four wheel and tyres the same size?
 
Mighty strange!
Do your brake lights come on at exactly the same time every time and when expected?can you ever press the brake pedal without the lights coming on? (May take 100 goes mind)
 
Howey said:
Mighty strange!
Do your brake lights come on at exactly the same time every time and when expected?can you ever press the brake pedal without the lights coming on? (May take 100 goes mind)
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I’m fairly sure they do, I had 2 iffy brake switches, both put the glow plug light up, the last green switch seems good, lights come on ok
 
Howey said:
Are you able to see all vehicle speed sensors whilst driving?
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I probably could, I could go for a drive connected up and monitor it. I’m really new to the whole computer, abs stuff, the Audi is my first and it’s a big learning curve!
 
Well if the four wheels are the same size and the tyres are all the same exact size i.e. width and profile that would rule them out. If one wheel is wider or narrower or a tyre is different the car will see a different wheel speed.

Double check those new tyres are all IDENTICAL.
 
Catnip64 said:
Were you monitoring the ABS module whilst driving? If you were it constantly sounds a warning, so this is normal.
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Aaaah!!!! Yes! I did!! Brilliant, that answers that one, on the final test I unplugged it, and when I set off again it stopped. THANK YOU!! Every day a school day!😀
 
So now that we’ve got to the bottom of the constant beeping ( due to me beta dumbass) I will take it out tomorrow to see if my 7mile beep is still there, which I’m sure it will be.
 
An update on this for future reference…..

So, after replacing….
brake switch (x3)
all 4 wheel bearings
all 4 abs sensors
YAW sensor
replacement engine ECU
rebuilt ABS pump ecu
checking wiring, fuses.
new battery
I gave up!! I’ve been working in wales and not had time to get it to one of the specialists, and the mot ran out mid December 😨😨
I have a local ish garage who has a young lad Jamie who is a bit of a whizz with VW and Audi cars, he spent ages sorting out an immobiliser/ ECU issue with a friends polo……basically nobody could sort it, and he took it on as a personal challenge. So for the first time since I was 17, I took a car to a garage for repairs and Mot if he could sort it……and he did!
TURNS OUT IT WAS THE ALTERNATOR!!
Although giving charge, it would dip after a certain period and cause all these issues, so glad it’s behind us now!!
 
The three beeps is low battery voltage but alternators wear and so charge at a lower voltage and don't tend to drop off and then climb again themselves unless the engine earth is suspect

On my previous post I had assumed you had already checked the engine to chassis earth which is an absolute must for all A2 owners the moment the car is purchased. If your earth was good then it sure was an odd fault
 
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Howey said:
The three beeps is low battery voltage but alternators wear and so charge at a lower voltage and don't tend to drop off and then climb again themselves unless the engine earth is suspect

On my previous post I had assumed you had already checked the engine to chassis earth which is an absolute must for all A2 owners the moment the car is purchased. If your earth was good then it sure was an odd fault
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Yes, definitely all earths were good, battery end, earth behind headlight to starter, and both on each a panels in the footwells, all removed cleaned up and good. So yes, a very odd one.
 
datsundrew said:
Yes, definitely all earths were good, battery end, earth behind headlight to starter, and both on each a panels in the footwells, all removed cleaned up and good. So yes, a very odd one.
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Was the earth from chassis to engine tested via its resistance? They corrode inside usually half way down, visual check is not thorough enough sadly
 
Howey said:
Was the earth from chassis to engine tested via its resistance? They corrode inside usually half way down, visual check is not thorough enough sadly
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I added a new one to the theory, but it made no difference, so took it off again 😨
 
Yes I did but looking to see if anything could be causing the alternator trouble.

You did understand my question about the BATTERY earth lead to the chassis? If so tell me where it is.
 
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