ABS Warning Light

M

mac911rs4

Member
Morning community.
Took the A2 on the school run this morning, and as per yesterday, was an effort (not too much) to start. Thought it was because we hadn't used the car for around a week, but then around a mile or so into journey, flashing lights appeared on the dash along with a series of bleeps, ABS light has come on and stayed on.....any suggestions greatly appreciated, more so as i've got the school run later too....
thanks in advance for any help.
cheers, M
 

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mac911rs4 said:
Morning community.
Took the A2 on the school run this morning, and as per yesterday, was an effort (not too much) to start. Thought it was because we hadn't used the car for around a week, but then around a mile or so into journey, flashing lights appeared on the dash along with a series of bleeps, ABS light has come on and stayed on.....any suggestions greatly appreciated, more so as i've got the school run later too....
thanks in advance for any help.
cheers, M
Click to expand...
Does it clear when you turn the ignition off and restart? If so I would try the school run, if not don't.

Mine did this about 5 times over a month and then the problem went away and has not returned in five years.

Andy
 
Andrew said:
Does it clear when you turn the ignition off and restart? If so I would try the school run, if not don't.

Mine did this about 5 times over a month and then the problem went away and has not returned in five years.

Andy
Click to expand...
Fingers crossed Andy, was about to go the local Inde, car's clear as anything, no issues. Gave it blast speed and braking wise, no issues at all. Will still get to the Inde tho and get it checked via vagcom, better safe then sorry....
 
So, no issues at all after restarting the car, driven it hard, braked hard, no issues whatsoever, although, heres the code i got from my local Inde, anyone had one of this intermittent problems.....?
 

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Same thing happened around a month ago to me, cleared the same day and not returned? Due a service shortly, will have it scanned at the same time. I fear the old girl is of an age (and mileage 191k) where electrical gremlins occur
 
I have had the ABS light come one a few times over the years. It was put down to a bad repair job on the cable the last time I took it in to an Audi specialist who fixed it but said that I would have to get a new loom eventually. I have just also had a brake sensor connector pin corrosion issue and am waiting for a replacement connector if one can be had. The ABS light has also started coming on again and if it's an issue on the same side I might just have to go for the new loom unless anyone watching this thread has any advice.
 
Agree with most, mines cleared entirely and performing well again. Think it may have been through lack of use and, as you say, they are getting on a bit.....thanks for replies anyway, fingers crossed no more issues....
 
mac911rs4 said:
So, no issues at all after restarting the car, driven it hard, braked hard, no issues whatsoever, although, heres the code i got from my local Inde, anyone had one of this intermittent problems.....?
Click to expand...

Hi,

I had that fault, its cause is the micro switch inside the brake servo. It could be a wiring issue but the switches do fail so its probably the switch rather than the wiring to the switch. You can check the wiring between the connector at the brake servo and the ABS unit plug to rule that out.

The switch is used to check the position of the brake servo piston as the ABS unit uses a solenoid to move the piston and apply brake pressure in situations when the brakes need to be applied but the driver isn't pressing the pedal (e.g. stability control). If the ABS unit sees the switch not operate in time with the pressure sensors it will disable itself and display the warning you are seeing. The ABS resets when turned off and back on again so as the fault is intermittent, it will be OK after you stop the engine and restart, until it happens again.

I lived with it for a few years (it was a "feature" of my car when I bought it) but eventually decided to fix it. You have to replace the brake servo as the switch inside is not serviceable. Unfortunately a new one isn't cheap but mine has been been fine since. My mechanic broke open the old servo to look inside at what was wrong (warning, very large spring inside!), its just a cheap micro switch. The problem is you can't get at it without splitting the servo in half and its not meant to do that! Later applications of that ABS unit have a servo with a removable and replaceable switch. My mechanic said that he regularly changes replaceable switches in VWs.

If it doesn't happen often and you are happy to live with it then you can leave it as it is. The ABS will be off when the lights are flashing but will be back working again when reset (switch off power and back on again).

regards

Andrew
 
Wiring to F83 / F84 - the switch and solenoid are on the same connector.
F83 wiring.png

Pin numbers for ABS connector.

ITTMK20Pins.png
 
Au2ro said:
I have had the ABS light come one a few times over the years. It was put down to a bad repair job on the cable the last time I took it in to an Audi specialist who fixed it but said that I would have to get a new loom eventually. I have just also had a brake sensor connector pin corrosion issue and am waiting for a replacement connector if one can be had. The ABS light has also started coming on again and if it's an issue on the same side I might just have to go for the new loom unless anyone watching this thread has any advice.
Click to expand...
I think this is the replacement loom you mean, it's not short by the way, 2.5 metres.

Hope the information is of use.

Andy
 
ajsellors said:
Hi,

I had that fault, its cause is the micro switch inside the brake servo. It could be a wiring issue but the switches do fail so its probably the switch rather than the wiring to the switch. You can check the wiring between the connector at the brake servo and the ABS unit plug to rule that out.

The switch is used to check the position of the brake servo piston as the ABS unit uses a solenoid to move the piston and apply brake pressure in situations when the brakes need to be applied but the driver isn't pressing the pedal (e.g. stability control). If the ABS unit sees the switch not operate in time with the pressure sensors it will disable itself and display the warning you are seeing. The ABS resets when turned off and back on again so as the fault is intermittent, it will be OK after you stop the engine and restart, until it happens again.

I lived with it for a few years (it was a "feature" of my car when I bought it) but eventually decided to fix it. You have to replace the brake servo as the switch inside is not serviceable. Unfortunately a new one isn't cheap but mine has been been fine since. My mechanic broke open the old servo to look inside at what was wrong (warning, very large spring inside!), its just a cheap micro switch. The problem is you can't get at it without splitting the servo in half and its not meant to do that! Later applications of that ABS unit have a servo with a removable and replaceable switch. My mechanic said that he regularly changes replaceable switches in VWs.

If it doesn't happen often and you are happy to live with it then you can leave it as it is. The ABS will be off when the lights are flashing but will be back working again when reset (switch off power and back on again).

regards

Andrew
Click to expand...

May I ask from where did you get a new brake servo and at what cost?

Is the brake servo identical for petrol/diesel?
 
ajsellors said:
Hi,

I had that fault, its cause is the micro switch inside the brake servo. It could be a wiring issue but the switches do fail so its probably the switch rather than the wiring to the switch. You can check the wiring between the connector at the brake servo and the ABS unit plug to rule that out.

The switch is used to check the position of the brake servo piston as the ABS unit uses a solenoid to move the piston and apply brake pressure in situations when the brakes need to be applied but the driver isn't pressing the pedal (e.g. stability control). If the ABS unit sees the switch not operate in time with the pressure sensors it will disable itself and display the warning you are seeing. The ABS resets when turned off and back on again so as the fault is intermittent, it will be OK after you stop the engine and restart, until it happens again.

I lived with it for a few years (it was a "feature" of my car when I bought it) but eventually decided to fix it. You have to replace the brake servo as the switch inside is not serviceable. Unfortunately a new one isn't cheap but mine has been been fine since. My mechanic broke open the old servo to look inside at what was wrong (warning, very large spring inside!), its just a cheap micro switch. The problem is you can't get at it without splitting the servo in half and its not meant to do that! Later applications of that ABS unit have a servo with a removable and replaceable switch. My mechanic said that he regularly changes replaceable switches in VWs.

If it doesn't happen often and you are happy to live with it then you can leave it as it is. The ABS will be off when the lights are flashing but will be back working again when reset (switch off power and back on again).

regards

Andrew
Click to expand...
Fantastic, thanks Andrew. Yeh it is liveable, in the near on one year we've owned and looked after the car, not had any great issues and this error has only happened once. So...until the next time. Thanks for the help, i'll pass onto my Inde for when it goes in if it happens again. All the best, M
 
Olerype said:
May I ask from where did you get a new brake servo and at what cost?

Is the brake servo identical for petrol/diesel?
Click to expand...

Hi,

the brake servo is the same no matter what engine. What makes a difference is which version of the ABS unit you have MK20 / MK60.
The switch and solenoid are only used by the earlier MK20 unit I believe. The later MK60 has a pump to generate brake pressure I believe so don't have the arrangement on the brake servo and so cannot have this fault. (That doesn't mean the MK60 is better, the pump can fail requiring a new ABS unit!)

The servo isn't cheap. I bought a new one from Audi for about £400 a few years ago. Its an A2 only part. That's why I didn't replace it straight away. You can get them from breakers very cheaply but unless you know the history, a second hand one could be a just as bad or worse then the one already in the car.

regards

Andrew
 
I had last year a similar with ABS light on cluster instrument. But after replacing the battery the problem disappered. Now since few days I have the problem again. Once turning key and run engine on I see the ABS and ESP lamps on. I have to turn off engine and restart it to get lamps off.
I have checked with VCDS. Sometimes I see on 03 all sensors front and back, left and right , and sometimes only front ones or back ones. The error is always the same " signal out of tolerance ".
So the question is: could it be possible that all four sensors are faulty or might I have a problem on servo brake that creates the error ?
Thanks !
 
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