Passat 2001 1.8T - ABS Warning Light On!

[richard child]

I have a Passat 1.8T (35,000 mile) my problems have started since the car overheated on Christmas eve. The thermostat was replaced , this did not cure the problem , so next was the water Pump. This was replaced onlong with the cam belt , tensioner etc etc. Since that time the ABS warning light stays on and also the handbrake warning light (red exclamation mark). The mechanics that carried out the work stated this was caused by the front wheels rotating (whilst the engine was warmimg up and front of car jacked up) and the rear wheels still stationary , causing the ABS ECU to throw a wobbly. They tried various resets but still the same fault. I am now awaiting a VAG diagnostic result.

Has anybody come accross this type of issue before? or am I looking at an ECU failure ? If I need a replacement can I buy a refurbished unit as VW brand new is over £600

Richard

[Dave Elcome]

This could well have been me asking the question.

I haven't had the problen exactly as you describe, mine was after an air bag light came on. A local independant VW garage scanned the system and told me I needed a new slip ring behind the steering wheel. This was duely ordered and fitted by them, but after fitting the new sensor the ABS lights are on, they connected up the test gear again, and stated that the codes for the ABS module had reset themselves to 0000, and that the only way to get the correct codes was to take the car to the local franchisee.

The car went to them, and they apparently dowload the correct codes from VW? but then said that the ABS module now had an internal fault, and would not accept the code, they quoted me £800+ for a new unit. I took the car back to the independant who is now trying to get a new unit from Euro car parts.

I wait with baited breath.

[auiron]

I have a Passat 1.8T (35,000 mile) my problems have started since the car overheated on Christmas eve. The thermostat was replaced , this did not cure the problem , so next was the water Pump. This was replaced onlong with the cam belt , tensioner etc etc. Since that time the ABS warning light stays on and also the handbrake warning light (red exclamation mark). The mechanics that carried out the work stated this was caused by the front wheels rotating (whilst the engine was warmimg up and front of car jacked up) and the rear wheels still stationary , causing the ABS ECU to throw a wobbly. They tried various resets but still the same fault. I am now awaiting a VAG diagnostic result.

Has anybody come accross this type of issue before? or am I looking at an ECU failure ? If I need a replacement can I buy a refurbished unit as VW brand new is over £600

Richard

Hi, this means that you're driving the car without ABS in operation. Perfectly OK as far as the law is concerned as 75% operation is all that is demanded. Unfortunately, you'r now driving a Passat with the road holding power of a Ford Cortina.
I had this happen to me and I put tape over the light for a time. An independent garage replaced a sendor unit on one of the front wheels, which was probably damaged when work was carried out on the brakes. Cost £115.20 on 31/12/03, on an A4.

[MalcQV]

Hi, this means that you're driving the car without ABS in operation. Perfectly OK as far as the law is concerned as 75% operation is all that is demanded. Unfortunately, you'r now driving a Passat with the road holding power of a Ford Cortina.
I had this happen to me and I put tape over the light for a time. An independent garage replaced a sendor unit on one of the front wheels, which was probably damaged when work was carried out on the brakes. Cost £115.20 on 31/12/03, on an A4.

Wow, a bit OTT. I owned a MKIII Cortina and it's road holding would not have been anywhere near as good as a 1.8T Passat (35k) without ABS/ESP.

They are miles ahead in suspension geometry/tyre technology now than they were in the 70's and early 80's

[richard child]

I have spoken to my mechanic today who states the VAG test shows faulty ABS module (no further details on that) they have ordered a replacement £780 !!! At the moment he has accepted liability and will cover the costs. Car in bits again and will be for a few days. More details as the story continues. My concern is are these ACU vunerable to power spikes or just expire at will

[Dave Elcome]

I have spoken to my mechanic today who states the VAG test shows faulty ABS module (no further details on that) they have ordered a replacement £780 !!!

Mine is still in the garage having the problem sorted out. He tells me he's ordered a new control mudule for the ABS from Euro car parts, it's a genuine Bosch part, but as it comes direct from Bosch rather than via VW it's £200 cheaper. Interestingly, he states that it's only necessary to get the electrical part which is £350.

He also keeps telling me that it's not his fault, seems strange that he's so 'willing' to pay for the part when "it's not my fault". Mmmmm

[Teutonic_Tamer]

Hi, this means that you're driving the car without ABS in operation.

Correct.

Perfectly OK as far as the law is concerned as 75% operation is all that is demanded.

Absoulte bollock$, and a dangerous comment. To start with the easy bit first - the 75% you quote is merely relating to the efficiency of the braking effect when tested on a rolling road during the annual MoT - period.

If you drive an ABS equipped vehicle on public highways, at any time with the ABS defective, then you are driving a dangerous and illegal vehicle. Be very warned, if you get stopped by the law, or have a prang, you will be in serious trouble.

The reason it is so dangerous to drive with non-working ABS - well I'll try and keep it simple. On cars (or vans, 4x4, trucks etc) without standard ABS, the braking effort to the rear wheels was restricted, either by a fixed rate pressure limiting valve, or with a variable rate load sensing valve. This was a safety critical system to prevent the rear brakes from locking under heavy or adverse braking. This maintained vehicle stability (if the rear brakes lock and the front don't, you will find your back-end starting to overtake the front!).

Now on vehicles fitted with ABS as standard, the rear pressure limiting or load sensing valves were deleted, and the necessary reduction in braking effort to the rear wheels is soley controlled by the electronics from the ABS system. As a result of this "better" control of rear wheel braking effect, manufacturers started to actually "over engineer" the maximum efficiency of rear brakes, by fitting much larger rear drums, and now with much larger rear discs (when compared to the fronts).

Now, if your ABS is faulty and not working (ABS light permanently on), the chances of doing an involuntary 360, even at relatively modest brake pedal pressures, will be much much worse than on the older pre-ABS systems.

Please be careful about the "advice" you quote here.

Rgds

[MalcQV]

Correct.
Now on vehicles fitted with ABS as standard, the rear pressure limiting or load sensing valves were deleted, and the necessary reduction in braking effort to the rear wheels is soley controlled by the electronics from the ABS system. As a result of this "better" control of rear wheel braking effect, manufacturers started to actually "over engineer" the maximum efficiency of rear brakes, by fitting much larger rear drums, and now with much larger rear discs (when compared to the fronts).

Now, if your ABS is faulty and not working (ABS light permanently on), the chances of doing an involuntary 360, even at relatively modest brake pedal pressures, will be much much worse than on the older pre-ABS systems.

Thanks, I for one was not aware the rear brake limiters have been removed on ABS cars. If you think about it logically it has to be removed, as the braking must be controlled by the ABS electronics.

[RDDarbishire]

[quote=richard child;12212]I have a Passat 1.8T (35,000 mile) my problems have started since the car overheated on Christmas eve

I have had a similar problem with my Audi A6 - I have spoken to ECU- repair.com and they think it is the ABS ecu unit which I have had removed by a local garage( 6 screws) and sent off for repair, the car still runs without the electronic bit of the ABS. They may be worth calling 01159190770 Roger is very helpful - I think it is a common fault with these Bosch units.

[Dave Elcome]

I have spoken to ECU- repair.com

Hi. is that the correct web address as I can't seem to find it under that?

hey may be worth calling 01159190770 Roger is very helpful - I think it is a common fault with these Bosch units.

Where abouts are they please?