Fault ABS Sensor Rear Left

[North2007]

Guys, this fault came up recently. Results in the ESP/ ABS warning lights and deactivated park brake. After changing the sensor, fault still there. Used VCDS to establish fault came up before wheels turned. Turned out a bad connection at the terminal ABS pump up front. Cleaned up the male pins, reconnected and fault gone.

[lordchris]

Thanks for posting.

I have a similar problem with front left. Have changed the sensor to no avail, I have a vcds log what would I be looking for for similar root cause ?

[North2007]

Did you check plug loom connecting to ABS pump?

[lordchris]

Not yet

Need to check :

Pins into sensor
Wiring to sensor
Plug loom - is this just the wiring?

Waiting for toddler to get to bed and hopefully I’ll get the car into the garage for a look! If it’s the cable moving it by hand should trigger the fault ?

[North2007]

If the fault comes up on start up before moving it’s the sensor, wiring or pump. If it’s triggers on rolling, it’s the ABS ring. Moving the loom may not trigger it.

[lordchris]

Sensor changed, fault back. Vcds showing faults with control module.

Confirmed by local mechanic. Came on this morning going over a speed bump.

Check pins?

[Architex_mA8tey]

If you end up changing the ABS unit (like I have) then make sure you get a "matching pair" ie the ECU and ABS part its bolted to come off the same car and have matching HW and SW numbers to your old unit. ALso to warn you, if you change it then you will always get a scanned fault code regarding the change when you run a scan - the only way to avoid this is to fit a brand new ABS module/unit and then it codes clear from new by Audi. But a second hand unit thats all working fine should cure the warnings coming up if its the old unit at fault

[lordchris]

ok thanks for advice will follow this. Still holding out hoping its the wiring.

Car is driveable atm, and putting this off till after xmas i think.

[lordchris]

Couldn’t resist another look at the wiring and good job I did.

Cable had a layer of tape on it which was hard to see initially, on peeling it off I found 2 cables which had previously been soldered and repaired. One loose and one completely split and disconnected.

Have no solder iron and need Car in morning, so had to improvise with a bit of wiring from a light fitting, duct tape, bandage tape and insulating cable. No doubt not fully water tight never mind it’s only twisted and taped but hopefully see me until I can get to auto mechanic.

Strange how 3 mechanics missed this... and all were asked and told which wheel it was.


Fault codes cleared in vcds, apart from control module defective; which I am led to believe can be caused by brake output tests in vcds. Apparently this fault can be ignored, time will tell.

[Architex_mA8tey]

Originally Posted by lordchris

Couldn’t resist another look at the wiring and good job I did.

Cable had a layer of tape on it which was hard to see initially, on peeling it off I found 2 cables which had previously been soldered and repaired. One loose and one completely split and disconnected.

Have no solder iron and need Car in morning, so had to improvise with a bit of wiring from a light fitting, duct tape, bandage tape and insulating cable. No doubt not fully water tight never mind it’s only twisted and taped but hopefully see me until I can get to auto mechanic.

Strange how 3 mechanics missed this... and all were asked and told which wheel it was.


Fault codes cleared in vcds, apart from control module defective; which I am led to believe can be caused by brake output tests in vcds. Apparently this fault can be ignored, time will tell.

Well found! that control module defective fault may well disappear once the car realises it is all working ok repeatedly