A4 2004 1.9TDI 230k km (150K miles)

2 weeks ago when i was going around 220 km/h on the highway the gear display (only PRNDS part of the display) suddenly disappeared(also the engine sound changed). I parked in a gas station and i stopped the engine. After I restarted the engine then my display lights all the warning signs, ABS, ESP, ENGINE and flushing BRAKE red light. I took the car on a truck to my home city back. Since it got cold (around a 3 hour ride) the signs go away at first starting of the engine. But when i go with the car 10 kms the gear display part again disappears. The the error codes said ABS missing message, TCU missing message(P1626).

Now i use the car. When i first start the engine motor warning yellow light on and then after 10 kms of driving the gear display disappears.

I changed the gear fluid (ATF) 40K kms before with the original Audi ATF of 4 Litres.

Is there any advice about the diagnosis of the problem? Is it related with canbus itself, voltage regulation or something epecially related to transmission control module?

thanks in advance

 

Since the ECM loses contact with both the ABS and TCM there is a good possibility that there is something wrong with the CAN bus circuitry.

 

First of all thanks for the reply.

Actually i am sceptical that the fault is "classical" AUDI multitronic failure. The TCM errors are either "flushing Gear display" or "all lighs on of the gear display". In my case it seems communication with the gear box control unit is completely missing. Also ABS module data is missing.

After this fault, I took the car to my technician 1 week ago, he took the TCU and brought it to an electrician who had expertise on multitronic TCUs. He said there was a problem in the pins of the card and fixed it. We took it back and put it into the car. But after warm up the same symptoms happended again (gear display disappearing). Electrician insisted that TCU is ok there was no other problem. We actually took the ECU and searched for an fault in the card but found nothing!

Actually my exact problem seems how can i diagnose the problem? a loose socket pin to the TCU, ground problem of CANBUS or what?

Does anybody have any idea or experienced this kind of gear display disappearing kind of multitronic failure?

Thanks a lot.

So how can i make a diagnosis on CanBus?

 

Ok TCU was the problem. It was replaced with a new (0 km) 2200$ TCU and the problem has gone.