GEARBOX TCU

[Ben_r1]

I couldn’t even tell you that difference to be honest. If it weren’t for this forum I’d have happily stuck good old red ATF in there.

[RS6Rottweiler]

I am interested in the comments regarding the F125 Switch, what fault or condition would imply that it could be this switch that is faulty rather than the TCU?

I noticed that when it happens the gear selector indicator on the screen is solid red with no gear selection showing and when it works only the gear that is selected is illuminated red. Is there anyway of checking this switch to confirm if it is working or faulty? I saw a video on You Tube and the guy was saying that corroded connections are an issue with this switch? How easy or difficult is it to check the connector as I suspect access is a problem or is the connector easy to get at?

I will get Vagcom connected and see what error codes it throws up and get back to you all

Thanks

[HPsauce]

Limp mode is what you're seeing. F125 can certainly cause that. Get those codes read before doing anything else.

F125 switch is usually internal wear/corrosion, though the connector can also be a problem.

[Drummerman]

I just had the F125 switch replaced when the car was serviced. Symptoms had been showing when starting from cold, putting it into drive , engaging with a bang and then all gear lights lit up.
Switched it off, started in neutral and then into drive - all ok. It did this nearly every morning but was ok later in the day. Took it up to Grizz for engine and gearbox service and to change the switch. Now sweet as a nut again.


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[RS6Rottweiler]

Thanks Drummerman, if you don't mind me asking what was the cost for replacing the F125 including labour?

My symptoms are almost identical, I have never tried starting it in neutral must give that a go, the main difference is it is very intermittent as to when it works or doesnt but like you it goes into reverse or drive with a bang with all lights lit up. Sometimes it will work straight off then fail later, very frustrating.

[Shoppinit]

F125 failure will generally throw an unambiguous fault code.