dakes2

The car is a 2002 A8 D2 Quattro 2.8 V6 AMX Engine. Uk SpecI have ran a test on the F125 multifunction transmission switch on my car with VCDS and the values of the measuring blocks should be Park - 1000 Z1-1100 Reverse-0100 Neutral-1110 Drive (D) 1011 , Z4 0011, the scan shows that these are all correct except for Reverse as mine is showing the measuring block value as 0000, could this be that the multifunction transmission switch is faulty, I dont know why its showing 0000 in the measuring blocks, when starting the car first thing in the morning I get a short pause of about 2 seconds when its put into reverse, then the bump and all the PRNDS lights come up on the dash and its in limp mode, if the car is switched off and started again all is fine and the car drives very well, I know its not a gearbox fault as it drives ok, its got to be an electrical fault, ive done a lot of reading up on this subject and my gut feeling is that its the F125 switch, can anyone give some input on why I am getting 0000 coming up in the measuring blocks for reverse gear selection

dakes2

UPDATE
I have now figured out why I am getting a reading of 0000 for the reverse signal, this means that the reverse is not getting a + positive power supply, upon taking apart the transmission switch I found that the electrical tracks inside the switch were worn and dirty, I cleaned them up and its working again, rather than put the old switch back I put a new OE ZF switch on the car and its working perfect now, anyone needing information on how to change this switch can contact me and I will give advice on it.

Samilcar

Thanks for updating. Our other car (1998 Jaguar VDP with the same transmission and switch) recently went into transmission "safe mode" caused by corroded F125 switch contacts. Looks like the lifetime of this switch is about 15-20 years and should probably be replaced/cleaned on a preventative basis. Luckily, the switch itself is able to be taken apart and cleaned after drilling out the aluminum rivets.

Oxnardo Ring

I've never known this-- do the other users of this ZF gearbox have the identical F125 switch used in the Audi?

Samilcar

The switch itself is identical to the RWD version of the 5HP24 transmission that Jaguars use, but the mounting tabs are slightly different. It would be nice if they were exactly the same, as the Jaguar switch is "no longer available".

Oxnardo Ring

Thanks for the info. Yeah, I'm sorta wondering when we aren't able to get certain critical parts like those to keep it running.

Saw on a Subie SVX thread the other day that certain SVX parts are almost unobtanium at this point-- it's going to be harder and harder to keep those cars on the road.
I don't remember the last time I saw a running SVX in fact.