ABS light arghhhhh!!

[andycowuk 0]

mine started coming on today, turned off engine, started again, all ok, drove around, it came back on, turned engine off, started, used abs...all fine, then came on a minute or two later.

 

I then reset it again and went up to silly speed out of town, and it stayed off, drove around town, on again.

 

there is no fixed time or speed to trigger the prob. what a pest.

[Henny 0]

mine started coming on today, turned off engine, started again, all ok, drove around, it came back on, turned engine off, started, used abs...all fine, then came on a minute or two later.

 

I then reset it again and went up to silly speed out of town, and it stayed off, drove around town, on again.

 

there is no fixed time or speed to trigger the prob. what a pest.

 

If you have any mechanical ability, it may be worth your time to take the rear disks off and check the rotor cages on the back of the disks... 8)

 

This is exactly what my G60 started to do not long after I got her, and it annoyed the hell outta me for ages until I changed rear disks and realised that one of the rotors wasn't attached properly and so occasionally stopped spinning at the correct speed causing the fault... :? :roll:

[akacheesy 0]

I had my mate plug in a fault diagnostic thingmagig into my C and it reported a voltage fault at the ABS pump. I am guessing that the ABS pump is FUBAR anyone have any ideas? I believe a MK3 Golf ABS pump is the same?

[h100vw 0]

That voltage problem at the pump could due to a bad connection. Maybe if you take the lpug off and refit it or check the condition of the earth wires around the pump. One may be corroded which would change the voltage.

I'd do stuff like that before changing the pump.

 

Gavin

[akacheesy 0]

Good idea Gav, might try that later. The guy who did my matrix told me that when he had the dash out he noticed that the ABS light had fallen out so he simply put it back and now I have this fault. i could swear blind thta it was working fine before it went in. Could his work have done something to make this happen do you reckon?

[h100vw 0]

Everythings a possibility. Maybe something was disturbed around teh fusebox, they are fussy things at the best of times. I spend a fair bit of time making sure everything works when I have fitted an alarm and had the fusebox out.

 

gavin

[dr_mat 0]

Ah, ABS eh? What a bag of pain it is!!

 

To add to the long list of woes above, mine is now showing some fairly constant symptoms that I don't like. I've not booked it in yet to get the error codes read, but here's the lowdown.

 

Turn ignition on - light stays on. Can drive off and the light will never go out (well that's working corrrectly then).. But having driven the car a short distance if I then turn the ignition off and back on, the light goes out and stays out for the rest of the journey.

 

Damned irritating, I can tell, cos it sounds like a loose conection, which is gonna be a complete git to track down I'm sure.

 

I intend to start going round checking the wheel sensor resistances, and re-seating the connectors, but wondered if anyone else had seen similar problems and found out what it was?

 

Cheers! :)

[Spykee 0]

Dr Matt,

 

i havn't found out what it is yet but i get a similar ABS light issure as you! it would be interesting to know what your C's prob is if you get it checked out.

 

mine has some funny clunking noise going on from the breakpedal in the footwell as well tho, i have already posted a thread on it a while back where some of the lads suggested some of the checks above as well as the rest of the sensors but i havn't got round to it yet cos the car is off the road.

 

i know for a fact that when thinking back to when i was driving it around if i was to jam on the breaks hard, so theoretically the ABS would kick in, then the wheels would lock but i would then get a big kick back from the break pedal which felt as if the the ABS would kick on for just one attempt?? the car stops bloody well when breaking from any speed mind but the pedal feels too spongy for my liking!? could it just be an air lock in the lines? :?

 

i don't know what the ABS on the C is supposed to feel like tho cos i have only felt it on newer cars like Vauxhall's, Chrysler's and Jag's. with those its like a judder from the wheels and the berak pedal!

 

i hope i don't have a serious prob, anyone else care to comment?? :?

[dr_mat 0]

I have been checking this out. One more factor to take into account with mine is that if you get into the car and sit there turning the ignition on and off, without touching *anything*, eventually the ABS light will go out normally, and from that point on it will go out every time you turn the ignition on. I had originally thought that it was necessary to move the car, but that is not the case..

 

This means it must be failing to pressurise the ABS cylinder due to the ABS pump not working 100% and taking longer than usual to prime the ABS reservoir. Now, that's a *bad* sign, cos they're DAMN expensive, but - it could also be the relay..!!!

If the relay is sticky these symptoms will be the same - every so often the relay unsticks, the pump runs, the ABS is primed, the light goes out. From that point on, it doesn't really matter if the relay fails again next time, cos the ABS is already up to pressure, so it doesn't matter...

 

At least that's what I'm hoping. Anyone got any better ideas or can tell me where the relay is?

[Joe M 0]

You could try cleaning up the contacts on the plugs at the front and right of the abs pump with some wd40. :?

[h100vw 0]

 

If the relay is sticky these symptoms will be the same - every so often the relay unsticks, the pump runs, the ABS is primed, the light goes out. From that point on, it doesn't really matter if the relay fails again next time, cos the ABS is already up to pressure, so it doesn't matter...

 

It does matter that the relay works every time. The pump should run, everytime the pressure switch senses that the system pressure has dropped. This would usually be after 3 or 4 applications of the brakes. You wouldn't hear it with the engine running.

 

If your relay was intermittent, then I would expect you to have tried the brakes and had a really dead feeling pedal.

 

Gavin

[dr_mat 0]

Hmmm. Clearly I need to speak to an expert, all this speculation is just wasting everyone's time! :(

 

So if there's pressure in the system, the pump doesn't run? Makes sense. So if you've turned the ignition on and the light has gone out, that means the pump has pressurised the brake system for you (or it was already at pressure). How does the engine's vacuum assist come into all this then?

[stormseeker 0]

Hmmm. Clearly I need to speak to an expert, all this speculation is just wasting everyone's time! :(

 

So if there's pressure in the system, the pump doesn't run? Makes sense. So if you've turned the ignition on and the light has gone out, that means the pump has pressurised the brake system for you (or it was already at pressure). How does the engine's vacuum assist come into all this then?

 

Vacuum or servo assist helps by reducing the amount of effort you have to apply to the pedal to produce a given amount of effort at the calipers. This has nothing whatsoever to do with ABS.

 

The ABS pump produces a pressurised reservoir of brake fluid that it uses to apply the brakes when it decides to take control away from the driver, because a wheel is locked/about to lock. The ABS brain uses a system of valves to allow the pressure from the brake pedal/master cylinder through to the calipers if it decides that all wheels are OK. The instant it detects a wheel locking up it switches a valve which reduces the brake fluid pressure to that wheel by switching in a reduced pressure from its reservoir. This reduced pressure allows some braking effort to get through, but releases the brakes enough to get the wheel spinning again. The ABS brain switches this in & out several times a second as long as you maintain pressure on the pedal and the affected wheels are locking up, hence the buzzing or vibrating you can feel through the pedal...

 

Hope that helps... :-)

 

have a look at http://www.ukcar.com/features/tech/traction/ABS1.htm for some background info...

[dr_mat 0]

That's what I thought...

 

I can't hear my ABS pump, by the way. The only noise I can hear is the one from the aux water pump. (Trust me that's what it is.) It's kinda tricky to have your head under the bonnet while you turn the ignition on...

[stormseeker 0]

That's what I thought...

 

I can't hear my ABS pump, by the way. The only noise I can hear is the one from the aux water pump. (Trust me that's what it is.) It's kinda tricky to have your head under the bonnet while you turn the ignition on...

 

I've never heard my ABS pump either - and so far (touch wood :-) ) it'sbeen OK... like yours the only noise I can hear under the bonnet when turning on the ign is the Aux coolant pump.

 

According to the Bentley Manual the system gives the ABS pump up to 60 seconds to come up to pressure before throwing an error... is this how long yours takes?

[dr_mat 0]

Nah, it's instant.

 

I checked the front sensors - 11k ohms, no worries, bang on spec.

 

I started the car this morning - ABS light on, drove round the corner, stopped ... got back in started it again - ABS light off. Drove like a loon all the way to work, and the ABS is not only working, but it's working perfectly (EDL funtion too). Repeated presses of the pedal don't faze it either, it just keeps working. Get out of the car at work, switch car off, press the pedal a few times (to hopefully trigger the ABS pump on next ignition start), turn the ignitiion on.. ABS light goes straight out, as normal...

 

Bloody bizzarre, I can tell you.

 

I can't find the rear sensor connectors (I've been told they're under the seats, but do you have to unbolt the seat-backs to access them?). Also, I had a look at the relay box, and can't see where the ABS relays and stuff live. The Bentley seems to suggest they're directly above the main fuse and relay box, but I couldn't find anything there.... Am I being thick?!

 

I *did* go to VW this morning to see about getting the codes read, but they are too busy. I tried Audi (next door), thinking they'd have the same tools, but they swore blind they wouldn't have the right equipment, so I left it at that... VW wanted to charge 30 mins labour to read the code (which would have been refunded if I'd gone to them to get the repair done) == ~ £40!!

 

Think I'll give my local independant a call...

[stormseeker 0]

The rear connectors come into the car under the rear-seat "bucket bits" (for want of a better expression :-) ) i.e. the bit your bum sits on, not the backs . AKAICR they just clip down so a quick sharp tug upwards should lift them up!

 

Just VAG-COM'd my ABS fault and it's 00793 Brake Pedal Position sensor - anyone know where that lives? On the brake pedal or on the ABS block? (just too lazy to get ETKA out at the moment... :-) )

[dr_mat 0]

Was your fault a solid fault or intermittent?

Mine is consistently inconsistent!

 

Oh and I did try lifting the seats, but they didn't wanna come easily, so I didn't wanna break anything by forcing it.

 

I think it's unlikely to be one of these sensors anyway, given the nature of the ABS light pattern..

[stormseeker 0]

Intermittently intermittent -

 

sometimes turning engine off/on will clear it, sometimes not...

 

sometimes goes weeks without lighting, then it's every day....

[stevef 0]

I have obtained a wiring digram and teat procedure for the Teves IV ABS fitted to post '92 VW's.

 

I have had to photo it so the qualityis poor but it is still readable and much better than nothing.

 

If anybody wants a copy they can PM me and I will e-mail it.

 

Cheers.

 

PS I also have wiring diagrams for the VR6 Engine wiring.

[dr_mat 0]

Ok, error codes are reporting:

near side front sensor fault

ABS voltage

 

the latter is surely what's triggering the start-up warning (duff relay?)

but I've no idea why the former has occurred - cos there's never a problem with the ABS when the engine is warmed.

I suspect the relay myself, but they're insisting it could be the sensor fault that's causing the voltage problem. (True enough, I suppose, but given that the sensor works perfectly for most of the time when I'm driving it I'm inclined to think not.)

[dr_mat 0]

I've asked them to reset the error memory and try it again later...

[awright182 0]

Dr Mat,

 

I think I have the same problem. ABS light shows a fault but if you go for a burn turn off the engine and back on again the problem goes away.

 

Checking the sensors revealed nothing. They are all in spec. If I put my meter across the other side of the connectors though I found that three of the sensors wiring back to the ABS unit are showing 100 Ohm but the RH Front is open circuit i.e no reading at all on the meter.

 

Once I've warmed up the car and the ABS is working all four connectors show 100 Ohm. I'm not sure what to try next.

Where does the wiring go? Does it go straight to the pump or does it go via some connector somewhere down by the drivers feet.

 

Anyone got any ideas?

 

Andy

92K VR6

[stevef 0]

For a start the sensors should read 1k to 1.3K or 1000 to 1300 OHMS depending on how you prefer your figures.

 

If you checked one of the sensors and it was OC then there is a problem!

 

From the ABS controller the sensors are connected pins 30+48 LHF, 29+47 RHF, 28+46 LHR and 27+45 RHR.

 

As far as I can tell the cables for the ABS sensors only have one join each between them and the controller. The fronts are on the strut tops and the rears under the rear seats (find the catch under the front edge of the seat base and give it a push with a screwdriver while lifting the seat).

 

The cables can be seen in the harness at the controller as all 4 are black and thicker than the others. I would remove the parcel shelves and the rear seats and try to get an idea as to how the cables are routed - through bulkheads etc - then follow them.

 

CABLES ALWAYS BREAK AT A POINT WHERE THEY FLEX, JOIN OR ARE SECURED. They seldom break if laying in a cable form that is not being moved or stressed. Look at the sensor ends, the joining connectors and where the cables pass through the bulkheads or are secured.

 

Hope this helps.

[Henny 0]

The front sensors also have a connector onto the sensor itself...