ABS !

Hi All.

My GTA turbo is fitted with ABS. Noticed on last couple of outings that at low speed the brake pedal had some resistance further down the pedal moment when moving at low speeds occasionally as if the ABS was kicking in. Today whilst out the orange ABS warning light came on as well but went out when the car was restarted. Also I have noticed today (but this maybe normal) if I start the car up with the brake pedal pushed down when the car starts up the pedal pushes back and grinds like the ABS is activating?

I have a GTA workshop manual but there is no section at all about where the ABS components are or how to fault find :0( Assume as this was only an option on later cars that is why its not in there?

A) Does anybody know what the issue is or how to fault find?
B) Does anybody have a understanding of where all the ABS components are ( I think the ABS pump is behind the radiator I have read which I assume is a front bumper off job)
C) Can you safely deactivate the ABS by pulling a fuse and if so will the warning light still come on? Most GTA's were not fitted with ABS and to be honest I cannot ever remember triggering mine even when driven on track?

Thanks for any advise.

Brad

[mettersl]

I have a copy of the abs supplement for the GTA with the wiring diagram. I can scan it for you but not for a couple of days,
Pump should be in the front right wheel arch, should be possible to disconnect by pulling out the 8 way? Multiplug near the horn air pump at the front of the right wheel arch under the boot liner.
Sounds like you may have a damaged reluctor ring on one of the wheels, or maybe dirty.
I'd start there looking for things that can mean one of the sensors is getting an intermittent signal.
The diagnostics on these systems is pretty much non existent, you have to check continuity of everything and condition by eye.
Best of luck.....

Thanks Lee

No rush for the ABS diagram but would be great to have a copy thanks .

The front brakes have been noisey last couple of runs out which would indicate that there is a lot of brake dust in them so hoping it's just a dirty sensor. I will take a look at the sensor and rings first . The sensors and the rings are behind the discs aren't they ? Also what is the best thing to clean up the sensors with ?

I also Want to be able to disable the ABS just to prove that it is the ABS and not something else ? Assume that's just a fuse?

Thanks
Brad

[mettersl]

I'll need to check on the fusing, wiring diagram will tell, abs may NOT be fused (safety innit). if you pull the plug I mentioned, it disconnects the whole ABS loom from the car.
At the front, the abs sensors are on the inside if the sub axle, you can see the teeth from the inside of the car looking out towards the hub.
Rears are on the end of the driveshaft, back of the hub.
I'd try brake cleaner as a starter.

Hopefully, I can scan it tomorrow. can you PM me an email address?

Cheers
Lee

Thanks PM sent

..... Does anybody have a understanding of where all the ABS components are ?

Brad ...... This may be of help to you, as Lee says, items most probably under the boot liner :-
Item
118 ...... ABS Computer
301 ...... ABS Electric Pump Assembly Relay
435 ...... ABS Solenoid Valve Unit
M18 ..... ABS Earth
R36 ..... ABS/Dashboard Harness

GTA ABS.JPG

Sorry ...... it does not want to attach as a Landscape pic, which the original is.

PS ..... Click on the pic and it gets rotated and bigger.

Thanks John most helpful. Think I'll check the sensors first and the earth (M18) as we all know to check your earths!

Think I'll check the sensors first

Yes ..... the rings must be kept clean and free from muck, but more importantly, the sensors are magnetic and can, over a period of time, collect ferrous dust which should be removed as it upsets the magnetic focus of the sensor. If the rings are rusty, they should be wire brushed so the teeth are their original clean shape.

Brakes have been squeaking quite a bit this year due to dust ( pads discs etc all good it is just dust) so hoping its just a build up of dust etc on end of sensor as you have said .

Cleaned up offside . Not worlds worst dirt wise. No damage to rings that I can see and will do nearside later tonight

Cleaned the off with some MAF(airflow Sensor ) cleaner that I had knocking around


Front


Rear

So all four cleaned now. And still happening. Not convinced it is the ABS as the ABS light has not come on since and think that may have been a red herring.

The symptoms are the brake pedal starts having a funny resistance at 3/4 of the way down but only when I am putting the car back into my garage up an incline and when in the garage moving forward very slowly. Took it out for a blast when I cleaned the senors and brakes were fine. Found a local industrial estate and stamped on the brakes hard a couple of time and managed to get the ABS to work , so the ABS is working. Went slowly round the estate and tried to recreate the pedal feel at slow speeds and it did not happen, everything normal. Brakes felt fine and performed fine. As soon as I goto put it into garage by creeping forward and braking as its quite tight I get the resistance every now and again (no loss of brakes just a resistance in the pedal?) Only thing I can think of is that a pad is binding and where it sits before going into garage it is getting hotter and binding more, but the wheels and brakes are not overly hot? No fluid loss either?

I've now convinced myself I am looking for nothing and should ignore it? Any thoughts on what it could be or if anyone has had the same?


Thanks
Brad

[mettersl]

Well, my smart does that where it has a missing reluctor ring tooth...caused by ABS coming on...only on light braking.
At least you now have an ABS manual for reference and clean sensors.
Failing that lube the pedal box and then change the master cylinder it's under 50 quid ...(Shared with a Renault master, so easy to source, when you know which one).

Cheers
Lee

Already lubed up pedal box and changed brake master cylinder a couple of years ago

It's bugging me that it only occurs in certain circumstance ? Not all the time when moving slowly toward