AUDI A4 PRDNS gearbox ECU repair

I had the PRNDS lights come up on my Audi A4 1.9 tdi. The car would randomly change from Drive to sport mode and i would have problems selecting reverse as well. I took it to Audi to get the full diagnosis. The Audi garage quoted £1300 to fix but i have managed to get the car repaired at half the price.

The problem is a switch in the ECU which controls which gear you are in when you select D. I found the following company BBA reman online catalogue online who said they could possibly repair the faulty ECU but i would need to send the ECU to them.

I decided it was worth a shot as it would only cost me my time to remove the ECU off the back of the gearbox and the postage and packaging to send it to BBA-reman for them to take a look.

Jack the car up on Axel stands/ramps or if you have access to a pit it will make life a little easier.
You need to remove the splash guard underneath the car so you can see the back of the gear box.
Drain the gear box of oil which will require a special tool which you ca get for £10 from draper Draper Expert 1/2 Square Drive Drain Plug Key For Vw Or Audi 63476 Draper Hdpk1.
Remove the electronic cable that connects onto the ECU that protrudes out the back of the back of the gear box.
The back of the gearbox has 12 torques holding the cover in place. Once you have removed most of them you will need to remove the rear engine mount to get at the last torque bolt at the top of the gear box.Support the gear box with a trolley jack so you can lower the gearbox to get at the last few torques.
The rear engine mount can be slid towards the back of the car so you can get at the back of the gear box. There is a couple of other bolts that you will need to remove that hold the ecu cable in place.
Once you have all the torques that hold the gearbox in place the cover can be slid off.
Once the cover is removed be careful not to bend the metal gasket as it cn be used again as long as its not damaged (Audi would probably change this along with the ECU seal).
Once the cover is off you can now see the ECU which is held in place by 3 torques or Star bolts.
After the 3 torques have been removed you can then slide the ECU off but be careful not to bend or tilt it as you remove it from the gearbox as it has guide rails made of plastic which can break easily.
To refit just follow the sequence above. The only problem I had was refilling the gearbox with oil!! Audi have designed the gearbox in such a way that it can only be refilled from a plug next to the drain plug underneath the car which requires a special tool which you can't buy!!

I found a local garage that had the special tool and they filled the gearbox with oil for me. I arranged for the car to be taken there on a trailer as the car cannot be towed.

The repaired ECU comes with a 2 year warranty once you get it back. I've been driving the car now for 2 weeks and there is no signs of the problems i was experiencing.
The total cost of the repairs was
£150 plus Vat & P&P
£120 for the refilling of the gearbox and clearing of fault codes
£40 recovery to take the car to the garage.

if you have any questions pleas feel free to ask.

cheers

Nick

...Bulletin Number: 0309
UPDATE PROGRAMMING (FLASHING) TRANSMISSION CONTROL MODULE (TCM). *TT

Bulletin Number: 0310
UPDATE PROGRAMMING (FLASHING) TRANSMISSION CONTROL MODULE (TCM). 2002 CABRIOLET INCLUDED. *TT...



...Bulletin Number: 0401
TIPTRONIC SWITCH F189, PRINTED CIRCUIT BOARD FAILURE. SELECTOR LEVER INDICATOR (PRNDL) LIGHT FULLY ILLUMINATED; TIPTRONIC FEATURE DOES NOT FUNCTION; 18152 TIPTRONIC SWITCH (F189) SHORT CIRCUIT TO GROUND. *TT...