ABS Control Unit

[Rob W 10]

I am currently chasing electrical faults around the car, but looking at the electrical diagrams i have (Bentley and Mitchell Repair), they both seem to be the same, but the reality of the wiring going into the unit is somewhat different. i am concerned that a previous owner replaced the Control Unit, which differs from the original, and has tried to re-wire it to work (but failed).

 

the serial number at the bottom is 1H0 907 379 E (10.0941-0321.4 3X1559).

 

i have attached the wiring going into the unit and how it differs from the circuit diagrams i have.

 

i feel that i need to start to chase wires to ensure that it is the same as the 2x diagrams i have. if any of you are able to assist or offer any thoughts or experiences with similar issues, i'm all ears. i only need to get this sorted, then MOT here i come.

 

many thanks in advance.

Edited May 4, 2018 by Rob W

[fendervg 33]

Are you sure you have the UK specific wiring diagrams? Most of the ones out there are for German or US cars. The Bentley will definitely be US only and the UK cars had an ABS system that was specific to RHD.

 

What is the symptom you are trying to fix? I'd say it's highly unlikely that someone will have rewired the unit, and unless they've been water damaged they rarely go wrong - most ABS problems are caused by faults elsewhere along the chain, most often the hydraulic pump unit.

 

I'll check the serials on mine and let you know what they are.

[Rob W 10]

do you have a UK electrical diagram, i could probably use that right now.

 

my issue is the light coming on intermittently. the sensors are all good. the hyd unit is good. looking at the wiring going into the ABS control unit, it looks like some one has soldered some wires together.

 

so i'm a little concerned that their is a fault in the wiring somewhere, i just don't know where right now.

[fendervg 33]

Afraid not, the only VR wiring diagrams are in German for a 93 car. The UK English versions have so far proven elusive - there used to be someone on here who had a stash of the dealer micro fiches and manuals, but I don't think they ever got around to scanning them all.

 

PM me with you email address and I'll send on what I have.

 

Did you scan the system with VCDS for fault codes at all? That kind of intermittent error with the light coming on randomly was exactly what I had, and the only thing that fixed it permanently was a new pump unit - there is a PCB and loom connector mounted to the bottom of it and this tends to get dirty, corroded and heat damaged because of its location and can lead to intermittent or temp related faults.

[tonedef 9]

I just found this thread on the forum from a few years ago, might be of use. http://the-corrado.net/showthread.php?76861-Abs-wiring-diagram

 

Years ago I had a full copy of Corrado wiring diags on loan from the local dealer to use while I was fitting my climate control, wish I'd copied it all at the time...........or just stolen it!!!

[fendervg 33]

Good find - I think they may be from the Bentley though (correction, it is a straight scan of the Bentley wiring diagrams, I've just checked my copy and the page numbers) - I don't see any mention of a brake pedal position sensor, which was a part specific to the system fitted to UK RHD VR6s.

 

These are for a US car.

[Rob W 10]

sorry, i have been away for a while.

 

i have put everything back together now. i'm confident that the wiring to the ABS ECU is fine now. annoyingly, after it was all put back together last week, i was able to drive it for some time at speeds upto 60mph without the light coming on. it was only when i stopped that the light came back on. i am know getting feed back through the pedal and can hear the pump working. same fault is back. frustrating!!!

 

i have already sent my ABS Pump to be checked and it was returned saying that all the valves are working correctly. as the fault is intermittent, i feel that the fault still lies within the pump. i'm aiming towards the PCB drying up. I'm taking it of on Wednesday to have a look, hopefully remove any oxidation deposits, then i am giving it another full bleed. i know it will pass an MOT with this intermittent fault, but its so annoying when you can't find the fault to repair it.