Hello, I have searched the forums here and have not found an answer. I have an issue with a 1998 A4, it is the 5 valve V6, Quattro, and equipped with the ZF Tip autobox.

It is throwing a hard DTC for "transmission vehicle speed sensor--G38", and goes into limp-mode if revved high enough. Reverse is normal.

I dropped the pan, and replaced the G38 speed sensor, fitted a new filter while I was in there, and refilled with the proper ATF. Problem still remains. My VAG-COM is on my laptop which is having issues, so I am using a borrowed VAG1552 tro scan the car. However I do not know the measuring block(s) for the G38 signal. I am suspecting maybe a wiring problem? The Audi techs at our dealership have never run across this one before.

I am a technician myself at Lexus, but my hobby is VW/Audi products, in particalur the TDI. However this problem is stumping me as well without the info. I know on our TDIclub forums many more problems are solved there than at any dealer, so that is why I am here

The car has a March of '98 production date, and has 103k miles. The old ATF looked normal (honey to dark brown color) and was not full of any debris. The car also has an ABS light stuck on, an airbag light on, and a check engine light on. There was no communiation at first until I disconnected the ABS module's electrical harness. The Audi guys said that is normal for a CAN bus communication failure if the ABS module goes bad. Then I was able to get a couple unrelated DTCs from the engine controller (evap sys gross leak, coolant temp out of range) and an airbag DTC (pass. side ignitor circuit malf.) as well as the above mentioned transmisison DTC of 00297-003 G38 no signal.

Any help appreciated.

 

Its possible one of the three wet clutches is dead. This would explain why the reverse works, because a different clutch is engaged for this.

If the transmission vehicle speed sensor G38 signal does not match with the transmission input sensor G182 signal, then your tranny is probably having other issues. Is the tranny slipping at all? Possibly a bad torque converter (slipping). The TC can slip if the N218 pressure regulator valve is faulty or if you don't have a fault code, it can be stuck mechanically.

 

Thanks for the info. So, what measuring blocks would I go to in order to compare the G38 and the G182 speeds? And wouldn't they be different in every gear?

What happens is, after the car is started, if you put it in drive it sort of halfway engages. If you rev the engine, nothing happens. It needs to be revved pretty high, over 4000 RPM, then it will "clunk" and go into limp mode...which I think is fixed 4th gear but not certain. I know it is a high gear, and the indicator in the dash goes solid.

If a clutch pack was cooked, it would seem the old fluid would have been loaded with debris and the filter would have had something it it. But the fluid looked decent. Darker than new stuff, but it did not smell strange nor have anything chunky in it. I cut open the old filter and found nothing, the magnets had very little metal on them and it was all a very fine poweder.

I hope these transmissions don't have short lives, because I just last year bought an '04 Passat TDI, and you must get the autobox with that engine...normally I prefer to drive a manual.

 

yeah I had thought about the fluid too. If it had been filled with material then I was sure it would be the clutches.
But even so, it is a common reason for tranny limp while reverse still works.

These tranny's are actually fairly resilient. You do not see many of them die. I'he had 2 tiptronics
and both were fine. My first got to 114K without any problems before it was totaled.

I am not sure which banks to read on the vag since I have never had the need to measure mine.