Corrado G60 1992 ABS problem

[Youngsyt 0]

Hi

 

I'm new to this and hope you will excuse me if I try and include all the information I have to hand at the moment.

 

I have a problem with the ABS light coming on. It has the classic symptoms of coming on when the car reaches approx 10 mph. However all the wheel sensors test OK at about 1100 ohms. The diagnostic readout shows fault code 01276 016 ABS hydraulic pump-V64 Signal outside tolerance. If I manually operate the pump relay ( which is located left hand side behind glove box ) the pump runs. I cannot hear the pump run at any other time. If I disconnect the plug attached to the end of the pump, the symptoms remain the same. Using a voltmeter on the pump relay I cannot measure +12v at any time on the terminal that should operate the relay. There is an earth on the other side of the relay coil.

 

All the circuit diagrams I have ( from the Russian sit and the Canadian Corrado club site ) do not agree with the wiring on the car.

 

Would any body be able to offer advice or perhaps the correct european wiring diagram for the ABS system.

 

The ABS pump and valve unit is located on the engine bay firewall ( right hand side looking from front ) underneath and to the rear of the expansion container for the radiator. The connector attaching to the pump has four connections. One is heavy gauge earth and the other heavy gauge for the switched positive supply. The other two connections are smaller gauge wire.

 

The ABS control unit is located behind the passenger side kick panel in the front footwell.

 

Things are getting desperate :( and any help would be gratefully received.

 

Thanks in advance

[Henny 0]

If ALL 4 of the sensors read about the same resistance, check your rear ABS cages... after a while they rust and stop sending the correct signals which sets the light on as the ABS has no idea what your rear wheels are doing... :?

 

The rear cages are about £10 per side including the mounting rings you need for them... ;) to change 'em it's a case of taking the rear disks off, and they then mount into the rear of the disk... 8)

 

(guess who's got the same ABS fault and has just found a new set of ABS cages in his garage indicating he never got around to changing 'em last time this happened... :oops: :lol: )

[Youngsyt 0]

Hi Henny

 

Thanks for getting back to me. Don't you sleep. :D .

 

I would agree with you on the sensor wheels if it wasn't for the single fault report from the ABS unit about the ABS pump. How can that be explained?

[Henny 0]

:oops: missed that bit about the fault code... :? I was probably sleep typing again... :roll: :lol: ;)

 

I can't help past that... sorry...

[Youngsyt 0]

OK . I've bitten the bullet and had a look at the offside rear sensor and cage. I picked the offside because an earlier diagnostic printout had shown it to be causing problems. This problem surfaced about a year ago but went away. Now the problem is reported as the pump.

 

From looking at it there doesn't appear to be anything obviously wrong. The cage is firmly attached to the rear of the disk and doesn't seem to be slipping. The sensor seems to be OK too although a little bit corroded where it goes through the back plate. Next step is to waggle ( technical term ) the wiring near the sensor while measuring the resistance at the connector under the rear seat. I'll do that tomorrow when I will have some help.

 

I've taken some pictures but can't post the images as I don't have a publicly accessable web server so I've attached them instead

 

Any thoughts?

[Youngsyt 0]

Looks like our posts crossed. Any idea where I can get the European wiring diagram from as I still think the problem is electrical. Thanks for your help so far :D

[Andy T 0]

Does the ABS perform the self test a few seconds after pulling away? You should hear the pump valves operating and a slight vibration through the pedal. Does the warning light coming on coincide with this?

 

I had a very similar problem, turned out to be the power cable to the battery had rattled loose on the terminal.

[Youngsyt 0]

That's the thing that I can't understand. When I originally had a problem some time ago, the ABS light came on when the ABS did it's self test at about 7 mph. At this time I felt the vibration of the pump running. When I had the ABS interrogated it reported that the rear offside whel sensor was not working. I didn't do anything about it and the problem went away.

 

Recently the warning light came on again and I had the ABS interrogated again. This time the fault reported was due to the pump. When the light comes on now following the ABS self test, the pump does not run. I've checked all the various connections associated with the ABS on both battery terminals. They all look OK and I've cleaned them up. As I said in an earlier post I can make the pump run by operating the relay manually. This would indicate that the main power feed and earth to the pump are OK. Getting the ABS light to come on is now completely repeatable. I can get it to come on at the same place on my drive ever time ( + or - a few feet ) and I get no vibration from the pump running.

 

I'm starting to believe that the problem is electrical and is due to the ABS contol unit. However I can't help wondering whether there is still a problem with a wheel sensor and the ABS unit is not running the pump during the self test because of it. As per the previous post all the sensors check out with the same resistance.

 

The trouble is that without a circuit diagram that is correct for the car I'm shooting in the dark. Another idea I had was that an earth had gone missing but as I'don't know where they are I'm shooting in the dark again.

[Henny 0]

if one of your wheel sensors has completely died (ie open circuit or no resistance) then this would cause the same kinda fault you report... however, if you interrogated the ABS brain, it would tell you that the sensor was dead, not the pump... :?

 

Got me well stumped matey... :|

[Andy T 0]

When I first had problems with my ABS, the light stayed on all the time, i.e it didn't go out after a few seconds after startup. This was due to a knackered wheel sensor. When it was replaced, the light went out after startup, then would come on later in the journey (due to a bad connection)

 

So I think you can eliminate a wheel sensor problem, because the if the light goes out initially it must of tested the wheel sensor circuit (?)

[Youngsyt 0]

I tried disconnecting one of the wheel sensors and the ABS unit saw it straight away because the warning light came on and stayed on.

 

Whatever is causing the problem is detected by the ABS unit when the vehicle reaches the magical self test speed. What I need to know is what does it test. It obviously checks the wheel sensors and assuming they are all ok ( I've only physically checked the offside rear ) that's not the problem. That leaves the pump.

 

Presumably the ABS control unit checks the pump by running it briefly during the self test. There are four wires coming off the connector on the end of the pump. Two are thicker than the other two and provide the main earth for the pump and the switched power from the pump relay. As I can get the pump to work by manually operating the pump relay, then the that wiring must be OK. That leaves the other two. It looks like they may feed signals back into the ABS control unit which would indicate whether the pump was running or not. There are also pressure switches built into the ABS valve block that the pump is connected to. I suspect that they also provide feedback into the ABS unit or aid in contolling the pump and the ABS main relay.

 

All this is good stuff but still doesn't explain why the pump doesn't run during the ABS self test.

 

It's looking more and more like the ABS contol unit is not asking the pump to run during the self test. I think the next step is to check the wiring between the ABS contol unit and the pump relay. That's not going to be easy without the correct wiring diagram.

 

I visited my local VW dealer today and having explained the fault they were puzzled but thought it sounded electrical in nature and suggested either the ABS control unit or looking for missing earths. They don't appear to have a wiring diagram

 

I love a good detective story - I just wish it didn't involve my car :D

[Youngsyt 0]

Well, I've just bought a second hand control unit and pump assembly which match my existing part numbes. Next step is to try some sunstitutions to see if I can nail the problem down. I still have not been able to get hold of a european wiring diagram.

[h100vw 0]

Do you have assistance on your brakes or is the pedal 'dead'. There is a pressure switch on the pump of LHD G60s (cannot be tooo different to a VR in principle), if it senses low pressure in the accumulator it runs the pump using the relay you have manually bypassed. I don't believe that the ECU can check the switch as there is no connection between the two. It may know some other way that there is something wrong cos it has a power feed missing??

 

On a LHD Golf/Corrado/Rallye the pump is run by the switch and the relays, the ECU has no control.

 

Gavin

[Youngsyt 0]

Hi H100VW

 

Thanks for your post. The ABS system for my 1992 RHD G60 is very different from the LHD system you describe. There is no pressure reservoir ( or at least I can't see one ). It appears that the pump provides the modulation of the brake pressure directly. There are some pressure switches built into the valve block that the pump is bolted to and it's possible that one of these is faulty. Without a wiring diagram is is difficult to tell. The only way forward I have is substitution using the parts I have just obtained. Thanks again for your interest.

[Youngsyt 0]

Forgot to say that the brakes work normally without the ABS. Pedal pressure hasn't changed. The contol unit I'm talking about is the ABS control unit in the passenger side foot well. I understand that the ECU isn't part of the ABS system. Thanks again for your interest.