ABS fault finding.

[Richard92 10]

Hello.

 

Corrado g60 1991.

 

My ABS light is constantly on. Yesterday we tried reading codes using a vagcom with a 2x2 adapter, no luck. It stated that it could not communicate.

From what I understand this usually means that the ABS ecu is shot?

 

Before i go out and buy a new ABS ecu, i would like to try blinking the codes.

 

I found a procedeure on this on the canadian forum, could anyone confirm if this is the correct approach?:

 

[ATTACH=CONFIG]82591[/ATTACH]

 

Connect the led test light between the +12VOLTS and the ENGINE

CONTROL.

 

Using the jumper wire connect the the - ground to the

ENGINE CONTROL for at least 4 seconds then disconnect.

 

The beginning of the fault code sequence is a single

flash followed by a 2.5 second pause. The next flash series

is the first fault code.

 

Fault codes consist of 4 digits

-1st digit evenly spaced flashes, 2.5sec OFF

-2nd digit evenly spaced flashes, 2.5sec OFF

-3rd digit evenly spaced flashes, 2.5sec OFF

-4th digit evenly spaced flashes, 2.5sec OFF

 

Each 4 digit code will keep repeating until the fuse is

inserted in the fuel pump relay again. When you remove the

fuse the second time the next fault code will flash, this

will continue until you insert the fuse again.

 

The end-of-fault display is signaled by a 2.5 second ON

light then 2.5 seconds OFF. This is known as code 0000 and

will continue until the ignition is turned off.

[Jim Bowen 1]

Some corrado ABS systems seem to talk to vagcom and some don't. Mine wouldn't work, i start to wonder if there is a wire that needs connecting up that maybe got missed in the factory, as when i fitted the teves20 abs system there was a single wire that i had to connect up for diagnostics to work.

[It's not a Scirocco 10]

Have you tried changing the latency on the port settings for the cable? Abs port on my vr6 only communicates if the port latency is around 4ms.

Also check resistance of each abs sensor with a multimeter.

[It's not a Scirocco 10]

Have you tried changing the latency on the port settings for the cable? Abs port on my vr6 only communicates if the port latency is around 4ms.

Also check resistance of each abs sensor with a multimeter.

[Richard92 10]

Maybe i'll give that a try, when i get my hands on a cable again. Cab port latency be set on an USB port?

What should the resistance be?

Also, if i slighty push the ABS relay, the light shuts of, then turns back on when i let go of the relay, normal or worth swapping the relay?

[robrado974 1]

Deffinately worth checking the connections to the relay and or , replacing it . Could be a cheap fix for you .

[MZpog 10]

Where is the ABS relay located?

[seanl82 23]

There are a 4 of them iirc, all located behind the glove box.

[MZpog 10]

There are a 4 of them iirc, all located behind the glove box.

 

Cheers, never noticed them before

[Richard92 10]

There are a 4 of them iirc, all located behind the glove box.

 

Does this apply for LHD cars as well? The ABS relay i was talking about is on top of the fusebox under the dash. Number 14.

 

 

EDIT: Maybe it only applies to VR models?

Edited November 4, 2015 by Richard92

[Richard92 10]

So.. I have so far replaced the 2 front sensors, as I measured them as dead. Also swapped the ABS Relay, because it was crap and the ABS ecu was burnt, so I replaced that as well..

 

The only difference from before to now, is that since I now have a functioning ABS ECU, the ABS light comes on after the system tests itself, not right away with when the power comes on.

 

After startup i feel a "click" in the pedal and the light comes on. Does anyone have an idea what may cause this?

[seanl82 23]

Only just saw the previous post so sorry for no reply. The relays I was referring to are for RHD VR6, so not sure what earlier models would have had sorry. I'd try scanning for fault codes again to see if you can now communicate with the ECU. Its possible there is a faulty valve on the pump, but have a go at driving it and stomping on the brakes a few times. I've heard it sometimes frees the valves up if they're gummed up a little. Worth a try I guess.

I feel your pain though, I had to replace a light unit, ECU, Pump, entire loom, 2 wheel sensors and the pedal position sensor before I had a working system!

[Richard92 10]

I have tried to blink codes, no luck. The test led just gives a constant light when i connect it, and it wont start blinking after using the jumper wire either. Weird.

 

Will try to connect the Vagcom after christmas time, as my mate who has the vagcom cable will be out of town for christmas holidays. Tho, I am unsure if the vagcom communicates with the 2x2 with only 3 wires, but we will give it a go anyways.

 

I use the car daily, the brake system is creating pressure and works, just the ABS part that wont work. Will try measuring voltage on the sensors tomorrow, but the resistance checks of all 4 is now good.

 

Where is the pedal position sensor located, and what does it do? If its not to expensive I might just change it as a precaution. Can I do any electrical testing on it to see wether it is defective or not`? Do you have the PN for it?

 

Im also going to look through the bentley to see how i can manually measure the solenoids, im sure i've seen some abs fault finding guide in there.

Edited December 22, 2015 by Richard92

[seanl82 23]

I sold my spare a few days ago and can't find it on vagcat so don't know the part number sorry. Its located on the brake servo directly under the master cylinder. Its possible to refurbish them too as its usually the electrical contacts that break internally, that is if you're comfortable pulling it apart as its bonded together.

 

Also, the VR6 I sold at the beginning of the year had the 2+2 connector and it communicated with vagcom ok.

[Richard92 10]

i found it: 357927810. Just to make sure: this is solely a electrical connector, and changing it will not open the hydraulic part of the brake system in any way?

[seanl82 23]

That's correct, its just a potentiometer i believe.

[robinw 0]

Hi. I had a problem with my light coming on intermittently. A check on the vagcom confirmed a sticking valve. As a first solution, prior to having the abs pump refurbished, I changed the brake fluid to clear out any possible contaminants and bled the system. This solved the problem and the system operated perfectly with the light coming during the test phase and then going out.

[Richard92 10]

Just a simple flush of the 2 front circuits and the rear circuit, or is there a way to flush the pump itself as well?

[seanl82 23]

You'll need to do the entire system, a vacuum pump is recommended as the cars are notoriously difficult to bleed. Ensure you do the pump as well (bleed nipples on the top) and the master cylinder last. Just open the bleed nipple on the master cylinder and let it drain out by gravity mate.

[Richard92 10]

Well.. I have now run trhough all the electrical tests as per workshop manual, except the operational checks of the valves, as I felt insecure of how to do them with the bridging and multimeter.

All electrical checks and values are OK.

 

The exact sequence of the abs light on cold startup is; ABS light on on startup, ABS light goes out, brake warning light goes on, brake warning light goes off, ABS light comes on and stays on. Any takers?

[ryan_welshman 10]

Anyone know if any part of the abs system relies on the rados main ecu or if its a closed circuit between the sensors and abs ecu alone?

[seanl82 23]

It does connect to the main ecu but pretty sure it's for diagnostic information only. Don't think the main ecu has any control what so ever over the system.

[ryan_welshman 10]

Thats good to know. I've got aftermarket ecu in now as im running on 45 dellorto carbs, so ill see if its sensors im havin problems with. The abs light doesn't come on at all apart from a split second flash where you turn the key off

[DanBert 0]

Hey Richard, I got exactly the same problem on my corrado. I would like to know, what was the problem and how did you solve it 😎 thanks man