Antilock warning light - ABS Pump anyone?

[Tom]

I've got the dreaded "Antilock light comes on at about 6mph, no groan from accumulator" problem on my S2. My garage has investigated as far as possible and concluded that the sensors are all working and so they suspect the pump. Their ABS tester is broken, so the jury is still out but they have tried all the usual things like replacing the two relays on the pump and cleaning the earth points.

Can anyone comment on the whether the pump is the most likely culprit? If it is the pump, I'm wondering whether anyone can advise a cheap source of parts or has a spare ABS pump they want to sell. The Bosch part number is 0 265 200 038 apparently.

History of problem

- The light first came on when I was driving fast round a bend
- Since (several months) it has come on and stayed on as soon as the car reaches about 6mph
- VERY occassionally, the accumulator groans and the the light doesn't come on, but then when I first apply the brake (gently), the pedal feels higher than normal and pulses weakly as I stop - then the antilock light comes on and stays on.
- Even more occasionally and not recently, the lights doesn't come on and everything works as it used to until the next time I use the car.

 

[Riverside]

I had the same symptoms with mine for a while, eventually diagnosed by substitution & it turned out to be the ABS ECU. It's easier to replace the ECU than the pump so imo try that first if you've already discounted a faulty wheel sensor.

 

[quickrich]

my abs light never goes out, is that more likely to be ecu?

 

[nick3814]

I've had this problem for a while, mine started coming on when I drove through a large puddle, a right pain in the ****! After lost of testing sensors and changing a couple I got sick and just disconnected mine, the brakes still work as normal, I found a thread on Pelican parts on how to disconnect them, the dash light goes out as well;

http://forums.pelicanparts.com/showthread.php?t=325059&highlight=abs

got through mot the other day also, I was told that as long as there was no warning light it would pass []

 

[Riverside]

ORIGINAL: quickrich

my abs light never goes out, is that more likely to be ecu?

Might be, or it might just be a broken wire, short circuit or a faulty wheel sensor. The wires to the wheel sensors are the most common failure point where the light never goes out but it could be something else. I took mine to my indy to diagnose, all I did myself was check for obvious physical damage to the wires.

Not sure how an insurance company would take it if I had an accident & my abs wasn't working, I guess maybe they would assume it broke in the crash (unless there were skidmarks). I have a good idea how they'd react if it were obvious I'd disabled it without telling them though.

 

[nick3814]

Thats not the kind of investigation an insurance company would carry out on a vehicle unless they strongly suspect you were at fault and you were claiming otherwise! Plus they would get that info from a police report and if the police are involved to that extent then you would have more to worry about than your ABS being unplugged.

Anyway its easily avoided, just don't drive like a berk!! []

 

[D7MPJ]

My ABS light is on and the large brake warning light that i asssume is ref the handbrake? (red) in middle of dash, i have only just bought the car and the discs and pads were knackered, i have replaced now but was hoping the light would go out, any suggestions on my likely cause?

 

[Riverside]

ORIGINAL: D7MPJ

My ABS light is on and the large brake warning light that i asssume is ref the handbrake? (red) in middle of dash, i have only just bought the car and the discs and pads were knackered, i have replaced now but was hoping the light would go out, any suggestions on my likely cause?

I'd guess it's the pad wear warning light maybe?

The brake pad wear sensors work by having a closed loop of wire which makes a circuit. Once the pads wear down to a certain point the sensor wire wears through & breaks the circuit. Just replace the sensors, or make the circuit another way if you are happy to live without pad wear sensors.

 

[Riverside]

ORIGINAL: nick3814
Anyway its easily avoided, just don't drive like a berk!! []

Yes I expect you'll be just fine, I'm sure you're an excellent driver. I wouldn't take the risk myself though, I'm one of those inferior drivers that occasionally makes mistakes.

 

[ashley]

ORIGINAL: nick3814

Anyway its easily avoided, just don't drive like a berk!! []

 

[James_G]

ORIGINAL: nick3814

Thats not the kind of investigation an insurance company would carry out on a vehicle unless they strongly suspect you were at fault and you were claiming otherwise! Plus they would get that info from a police report and if the police are involved to that extent then you would have more to worry about than your ABS being unplugged.

Anyway its easily avoided, just don't drive like a berk!! []

Good advice but alas the only time I ever invoke ABS on either of my cars is when those around me are driving like berks! So I wouldn't personally run my car without it.

 

[Neil Haughey]

Bad connection up near the wheel is probably most common cause, followed by ABS ECU and ABS relay. ISTR that over the past few years a fair number of us have had the ECU fail practically everyone at some point has had a bad connection and some ppl have had the relay fail. Some one reported they had replaced the pump but the pump wasn't the cause so this means I have never heard of someone having a failed pump. Garages like to say its pump as its easy to say somethings at fault without actually properly diagnosing it. Problem is that I couldn't find a way to test the ECU without an ABS tester so I swapped mine with a friend to determine that it was in fact the ECU that was dead.

Fast chargers/starter boosters and welding will kill the ECU's on these cars, I think a lot of ppl forget this. I used to use a fast charger fairly often so only my own fault I guess. The workshop manual says to disconnect the ABS ECU when welding for example.

 

[Tom]

Thanks to everyone for their thoughts - It sounds as though I shouldn't give up and get a new pump quite yet. Perhaps bad connections, broken wires and a faulty ECU need to be ruled out first. Is the ABS controlled by the ECU located under the footplate in the passenger footwell?

 

[Riverside]

ORIGINAL: Tom
Is the ABS controlled by the ECU located under the footplate in the passenger footwell?

IIRC it's above the boot release in the driver's footwell (on a rhd car). I have one in the same place on both sides, I can never remember which is ABS & which is the cruise control ECU without checking the part numbers []

 

[Tom]

Does anyone out there know the exact sequence of self tests that the ABS system completes? Mine only fails once the car is moving and based on the findings below, I'd like to know for certain whether a faulty pump can cause these symptoms...

After more than a year, three garages, two ABS pumps and a growing labour bill, I still haven't got this problem sorted. To summarise:

- The symptoms remain the same: Start the car, Antilock light goes out. Drive away and once you're above a few mph, ABS pump does not whirr, anti lock light comes on and stays on, ABS is disabled.
- All the ABS wiring has been checked with no faults found.
- The ECU has been swapped with another car. Mine works fine in other car and using the donor ECU in my car doesn't fix the problem.
- The ABS relay and those on the pump itself have been swapped. No impact.
- Wheel sensors have been checked with a multimeter. Apparently they all give similar readings which change when wheels are spun.
- The pump will operate if power is applied directly to the motor.
- The pump has been changed twice - The first replacement was faulty (would not pass hydraulic fluid through rear wheel circuit). With the second replacement behaviour is the same is before, no change to symptoms at all.

So either the latest replacement pump has the same fault as my original one or the diagnosis has been wrong from the start and the fault lies elsewhere.

Does anyone know for certain whether the pump (which consists of the solenoid valves and the pump itself) are part of the final check at 6mph?

Thanks for reading

Tom

 

[scam75]

Hi Tom

I have an ABS problem which I believe to be the pump. My light stays off as it should all the time (lights up with ignition then goes out as normal), pump whirrs happily but ABS is completely inoperative. This also happened to Super Marv's 968 and he had the pump replaced which cured the problem.

Therefore a faulty pump does not seem to light up the warning light whereas problems with sensors, wires, ECU's will.

So I would say your pump is fine and always was, the problem will be electrical.

Incidentally I need a working ABS pump if you have a spare!

Hope this helps

Stuart

 

[Tom]

Hi Stuart,

That's very interesting - not conclusive but another piece in the puzzle. I wonder if in your case the problem is with the solenoid valves in the pump, since your pump whirrs.
One reason I'm not convinced I have a pump problem is that I can't see from the wiring diagram how the ECU could detect a faulty pump - there is no obvious feedback mechanism from the pump or solenoids to the ECU.

I'll let you know if end up with a spare pump - Currently I have three!

Tom

 

[barks944]

If motion is what causes the failure, my guess would be that the ECUs test on the wheel sensors is showing a failure on one of the wheels. Each time you turn off the ignition the ECU will forget it has failed and wait until the next wheel sensor test before it realises theres a problem. Have you checked the teeth in the hub that the sensor picks up? My friends pug had failed abs and the pickup ring had fallen off.

 

[DavidL]

ORIGINAL: D7MPJ

My ABS light is on and the large brake warning light that i asssume is ref the handbrake? (red) in middle of dash, i have only just bought the car and the discs and pads were knackered, i have replaced now but was hoping the light would go out, any suggestions on my likely cause?

That's the exclamation one? If so that's the general warning light that comes on with any of the others that can light up on the dash - handbrake, oil level, brake fluid abs etc.
My abs light is also on permanently. It wasn't before the car was serviced last year so when it goes back in a month or two they can fix it! I've had a quick look at all the wires and it seems ok so I suspect the ecu.
Above the boot release button by your right knee as you drive as someone said.

 

[scam75]

ORIGINAL: Tom

Hi Stuart,

That's very interesting - not conclusive but another piece in the puzzle. I wonder if in your case the problem is with the solenoid valves in the pump, since your pump whirrs.
One reason I'm not convinced I have a pump problem is that I can't see from the wiring diagram how the ECU could detect a faulty pump - there is no obvious feedback mechanism from the pump or solenoids to the ECU.

I'll let you know if end up with a spare pump - Currently I have three!

Tom

Cheers Tom. I'm certain it's a a pump failure I have and you're right about the ECU being unable to detect a faulty pump.

PM me if I'm in luck!

Stuart