Audi CQ20V ABS problem

[Ivan_from_Russia]

Hello Tom!
You have solved the problem with the ABS?

[Tom_]

Hi, not yet because i dont drive car during winter (building engine), but when will be more warmer, i want to measure with osciloscope

[Tom_]

What good ABS relay suppose to have an resitance? The bigger one 4 pin have 44,5 Ohms and the small ones 5 pin have 81,5... What about relay under the dashboard? Fuse looks good. How much ohms is good for the ground on our cars?I checked ABS pump ground and it was around 3,0+- Ohms...



This abs problem is ****ing bother me...never ending story...

[Tom_]

shorty_94 M2ki dissasembly the ABS ECU connector and measure abs wires through body...On paper you can see pictures. I put away ABS relay and take there wire and ABS comes ON after few seconds after engine was started. But when i wiggle with that wire, ABS OFF and than after few seconds comes ON again...co i guess that relay is good.

And when the ABS comes ON, i can turn him off with ABS button on dashboard, so the button is good too i thought. But i cant turn ABS ON with abs button, when the wire was connected instead of abs relay



Any ideas guys?

[M2ki]

Button and lock switch on rear diff is connected to abs combi relay nr. 76

[Tom_]

Ok, so relay seems to be good..ABS ecu as well.

piotr Any ideas ? I am desperate

[Tom_]

Before a while i measure AC voltage on abs sensors with moving the wheel...I also check battery which have 12.8 Volts. Next i fill up the servo reservoir.. Brake lights is good...every fuse check with multimeter with a beep

FDriver front 0,71
Codriver front 0, 75
Driver rear 0,67
Codriver rear 1,1

Guys, what next?

[shorty_94]

Did you already check the sensor voltages with an oscilloscope?

[Tom_]

Not yet ..i think that problem will be in different place because when i start engine on idle for around 15 seconds, than ABS goes off and shows on gauge...

[M2ki]

ABS light turns on even when relay nr. 76 is briged with a wire, when stationary and idling?

[Tom_]

M2ki Yes, exactly...when is briged with wire and idling. :/

[M2ki]

Then you can eliminate faults at relay 76, abs switch, diff lock swicth and switch on the rear diff.
Maybe you have already measured wheel sensors ohms from the abs ecu connector, if they are similar, then probably no fault with sensors and sensors wiring.
Dont think the wiring inside the car is faulty.

You can bridge the pump relay to find out if the pump even works.

[Tom_]

M2ki Now i can eliminate ABS ECU, because i try my friends ABS ECU and problem is still there... I can eliminate ABS pump relays too, i try from the friends car and problem is still :/

I have already measured wheel sensors ohms from the abs ecu connector..

8-9 pin 1,181 ohms
11-21pin 1,258 ohms
26-24 1,173 ohms
22-4 1,193 ohms

U mean those relays inside abs pump?

[M2ki]

Yes inside the pump, one is for solenoids, other is for return pump.

If possible try your relays and ecu on your friends car also.

[Tom_]

M2ki Which pins to bridge inside the pump?