Hi All , Im new here so apologies if this is in the wrong place.
I have recently brought a 2005 A4 cabriolet 3ltr which has a problem. When i start it sometimes it appears to be in limp mode . if i switch off the engine and tap the selector and restart all is ok .
Any of you guys any ideas please ?

Hi. I have been having a similar problem with my A3 1.4TFSi. It has slowly been getting worse and this weekend it decided to stop running on the M5 (so called smart motorway). Thankfully it restarted and I got into the lay by.

The RAC said it had a low gearbox oil pressure warning and towed it home. The taxi driver said it could just need an oil and filter change. My local gearbox specialist said it wont be the oil, it will be the Mechatronics unit, its a common fault (£1250ish). My local garage said I can change the oil if you want me to.

Advice would be useful as I do not like car enough to part with £1.2k.

I would personally try the gearbox service first as you'd be surprised how many times this resolves the problem. In failing that you could find a used part but it might need coding to the car. 

Cheers

Steve

Update. I took it for the oil change but the guy said that there was oil leaking out of the Mechatronics unit gasket. He said it would be a specialist job to replace the gasket so I stopped the job.

Part ex'd the car now for a vauxhall. 

So I had a limp mode problem with my 2003 A4, after many garages and mechanics looking at it I’ve been told to get everything from a transmission fluid change to a new gearbox, however I decided to do some research on my own and I found that it was likely a component called a transmission range sensor that was putting it in limp mode. I found an after market one and had it fitted, that was about a year ago and it hasn’t gone into limp mode since. 
 

hope this is some help.

I got rid of it, part exchanged for a Vauxhall Mokka. Sshhhh

Fair enough! Didn’t see that part 🙂