Audi A4 Cab 2.5 TDI V6 engine cutout, esp abs lights flashing prnds on dash

[Sayed123]

Hi all, I have recently bought an Audi A4 Cabriolet 2.5 TDI V6 (100,000 Mileage, 2004, 2 Cambelt Changes) and within a day the car fails to start intermittently with the flashing PRNDS on dash. The ESP and ABS lights illuminate and the engine will crank over but the car fails to start! I have to either keep taking the key in and out until the flashing PRNDS goes back to normal (which can take between 1-30 minutes) or I have to wait about 15mins without attempting to start after which the car will usually start. Upon restarting, the dash will illuminate either the EML, ESP and ABS together or all 3 at once. Most commonly it won't illuminate anything at all as if there was no problem at all.

 

The worst thing is the car can suddenly cut out whilst driving and has done this everyday at least once or twice, causing the steering to lock and ESP/ABS lights to come up and the flashing PRNDS after which I will be stuck for upto 20-30 minutes trying to restart the car!

 

I took it to an Audi Technician who checked it on the VCDS and found only 1 major fault which was the crank position sensor (G28 Sensor - no communication) so replaced this immediately and also carried out a full service as this was due. He also found intermittent faults such as fuel pump and throttle valve and coolant temp sensor but said they were minor issues which would be rectified once crank sensor was changed. Problem still persists and has gradually got worse. Technician is baffled as to what it can be. He is sure that the gearbox is fine as he checked and said gearbox ECU is fine but can't connect to engine ECU as this is switched off when the problem occurs and also doesn't allow the VCDS to connect to the engine ECU.

 

He has a hunch that it could be the throttle valve motor which doesn't open the valve intermittently but this shouldn't cause an engine cut out surely?

 

There is no loss in performance when the car is driving, no juddering in R or D, no loss of reverse, idles perfectly, no excessive smoke, no mechanical noises, basically drives perfect as it should. I'm pretty sure it is a sensor issue but can't put my finger on it nor can the Audi tech. It's come to a point where I don't feel safe driving the car and only had it 2 weeks. The brake light on the gearbox doesn't illuminate when this problem occurs either and the brake lights on the car remain on constantly whilst the PRNDS lights are flashing and the ESP/ABS lights are on the dash despite me not touching the brake pedal.

 

The car has full service history but should have had a gearbox oil change 20,000 miles ago as only had one just before 40,000 but tech doesn't think this is the fault as he checked the transmission and there is no juddering at all when selecting gears.

 

I'm really confused and any help would be appreciated.

[Sayed123]

Please note,

 

the car is most prone to failing/ cutting out when the engine is warm ie. never fails to start in the morning or after leaving the car alone for over an hour or so.

[James]

If you read online about the flashing PRNDS it quite often turns out to be the gearbox ECU