I would really appreciate some advice with my A6 C5 2002 2.5 TDI.

Just had the TCU repaired and I re-installed it back into gearbox, following the fault logged by VCDS (17090 - Transmission Range Sensor (F125): Implausible Signal P0706 - 000 - - - Intermittent)

I did a short test drive before the car juddered and then PRNDS flashing on dashboard.

I 'limped' home and got the car back on my drive.

I now cannot connect to the TCU to troubleshoot:
Address 02: Auto Trans- Labels: 059-907-401-AKE.LBL Controller:
Note: Excessive Comm Errors

I did only manage to connect to the TCU a few times before the fault.

The TCU repair specialist is happy to test it for free, but I would rather connect to it first and diagnose (if possible).

Ross-Tech support have advised me to check wiring, but not sure how do do this.
I'm using a registered VCDS Lite with a Gendan USB KKL VAG diag cable. Connects OK to all other modules on car.

Any ideas and advice very welcome.

Thanks