Audi A4 B6 - ABS Module Coding "login lost due to dropped session"

[cmulindwa]

Hi All,

I hope someone can help me here!!

I have an Audi A4 B6 with an ALT 2.0 engine and CVT transmission.

A couple of weeks back it intermittently got ABS and ESP lights on, with no speedometer reading. It would report a front left hand side wheel speed sensor (G47) fault 00283. I cleared this fault but it kept returning. To confirm that it was indeed the LHS front wheel speed sensor that needed to be replaced, I swapped with the RHS wheel speed sensor but still got exactly the same fault. I also checked the reluctor ring on the driving shaft where the sensor picks its signal from and found it was perfectly ok.

I therefore suspected an ABS Module problem and tried to install a used one with a similar part number, but it didn't work, instead it threw up two faults 00778-Steering AngleSensor (G85) 66-10 Not matched -Intermittent and 01044-Control module incorrectlycoded 35-00 .

When I reinstalled my old module i found it was now also giving me the above two faults 00778 and 01044. It must have lost its coding in the process of removal and reinstallation.

I have tried to recode it using VCDS and following the Ross-Tech procedure (Login>Coding>G85 sensor calibration) but failed. I keep getting error message "login lost due to dropped session". The same happens when I try to code the second module I have. I am sure that I have generated the correct login code - the sticker in the boot indicates that the vehicle has 1LE braking system and a CVT transmission.

I will be most grateful for help with this problem.

Many thanks

Charles

[Alan02]

I`m replying on your ABS fault only. When you swapped the sensor and it still showed an issue on the left side, did you not investigate the vehicle wiring from the plug connector to the ABS? As this could be the issue?

[cmulindwa]

Many thanks Alan,

Yes I did test the wiring between the plug connector and the ABS, and there was continuity. Also forgot to add that I tested the wheel speed sensors using VCDS and I got consistent readings from all 4 wheels.

[Alan02]

That`s good, but did you also check for a short circuit on all of the wires? You will get continuity on a broken wire if it is shorted to another. Sorry if you have already included this in your tests, as you do not mention it.

[cmulindwa]

Many thanks Alan, I hadn't actually checked for a short circuit on all the wires as you propose. I should have done that. I only checked for continuity. However, luckily my problem is now solved. It turns out both ABS modules I had were faulty. I got a third one and was able to login and code it immediately without any error messages.

The hard bit was to bleed the brakes. At the beginning I fiddled with the ABS pump, trying to remove the module, I ended up opening 2 brake fluid tubes off the pump, which I needn't have done. This caused air to go into the system, which resulted in my brake pedal collapsing to the floor, when depressed, and requiring a bleed. I then tried to bleed the brakes manually, to no avail. It is after I run the ABS output test in VCDS that the ABS pump got triggered and it built up pressure in the system that is when my brake pedal hardened again. Subsequent to that I had another go at manual bleeding - following the sequence RR,LR,RF,LF just to be sure that all the air was out of the system. Everything is running perfectly fine now. But thanks indeed for taking an interest in, and responding to, my call for help.

[Alan02]

I`m pleased its all fixed now! It just shows you cant rely on 2nd hand parts to work!