Hi Guys
Sorted (I think)
I hope the information below will help others.
original fault was that my Audi A7 2011 started changing gears itself, changing from Drive to Sports mode with no demand from myself, quite dangerous.
On the dash I had the message "Gearbox Fault you can continue driving"
Called out the AA, who plugged in the computer and could see 2 gearbox faults but could not identify what they were, advised me to take to a garage.
Took it to the local Audi main dealer who eventually found fluid in the main electrical connector on the gearbox ECU and was charged £60 for the diagnosis.
Quoted just over £3k to replace the gearbox ECU and wiring harness. At this point I decided to look into it myself.
Took it to a friends garage and up on the ramp. removed the gearbox connector and yes there was the fluid inside the connector.
Here's a picture from the web, but looks identical
The fluid was obviously coolant from the colour and sweet taste (don't recommend tasting though..)
So far so good, but how did it get there???
Answer - From the Coolant control valve which is about 12" away and along the same loom.( My issue was from the coolant control valve, but it could have been another valve or sensor)
It is apparently a common fault with Audi's and an issue known to Audi- There is a Technical service bulletin out on this TSB# 2033806/7
The TSB is well worth a read.
Without getting too techie, The coolant control valve starts leaking fluid through the electrical connection point, this fluid then travels down through the harness through a process called "capillary effect" or "Wicking" and eventually gets to the gearbox electrical connector and causes mayhem to the CAN signals which control the gear selection process.
In my case, we used an airline to blow the coolant out of the gearbox connector (carefully on the gearbox end) then sprayed the connector with electrical contactor spray and reconnected the connector.
On testing the car, the error message has gone and no more random gear changing.
VCDS does not show any errors now.
I have a new Coolant control valve being fitted tomorrow ( £130 from Audi or £30 from ebay)
If the new valve is not fitted, the problem will just come back in the future.
Here's the kicker, had I gone with the Audi main dealer quote, a new harness and gearbox ECU for £3k, the quote did not include a new coolant control valve,
therefore I would have been £3k poorer and would have received a "temporary fix" as the valve would have continued to leak and eventually find it's way to the gearbox ECU connector again.
In the end it cost around £250 to get sorted.
Sorry for the long write up, I hope it helps others.
