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A6 bi-tdi possible gearbox issues, won't drive

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Hi new to the forum but desperately hoping someone has heard of this problem. 

Our A6 (3.0 bi-tdi 313hp, quattro, 8 speed auto gearbox) first showed problems when reversing into the driveway one evening. The electronic handbrake came on and the dashboard said there was a problem with the gearbox selection and asked us to select park then select the gear again. After 10-15 minutes of creeping back a foot at a time we parked up. 

Mechanic had a look at the codes and couldn't explain it. Got the RAC out and they suggested the issue was the boot sensor as it thought the boot was open. Hold the button for 3 seconds to reset and it would work again. Took it to the garage to replace the sensor but they couldn't get the same error and the car drove faultlessly. They suggested that the gearbox ecu might need replacing at a cost of £4k...

Drove around for a few days without issue, then on the way home the gearbox would move to neutral whilst underway (the gearbox selection on the dashboard would disappear) then back into the gear it had been in. 

Since getting home sometimes the car won't start but if it does it won't let you out of park and every error you can think of appears on the dashboard; start stop system, tyre pressure sensor system, handbrake system, etc... And the engine management light is on. Also, you can hear stuff happening below the gear selector as if its trying to either free it from Park or select something. Oh, and the electric tourneau cover no longer operates. 

I tried charging the battery to see if low voltage was causing a problem but it isn't that. 

Has anyone heard of this before or could point me in the direction of someone who can. 

Apologies for the length of the the post. Just praying someone can help 

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This may be related

 

Good luck.

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Hi Envy

Thanks for the link. I'll check it out. 

 

Can anyone tell me how to get to the coolant valve and connector? 

Then at least I can have a look and see if it's covered in coolant 

Cheers 

Barry 

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Hi Barry, my advice would be to get a gearbox oil change carried out as the c7 autos are known for not going into reverse if the oil needs changing

Cheers

Steve

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Your BiTDi will have the Multitronic Gearbox- Sorry cant help with location of connector and the coolant control valve.

Agree with Steve Q regarding the oil change regime of the gearbox but your cars random behaviour smacks of electrical signal vagaries. So many components connected by CanBus - the slightest shift in voltages on signal lines will cause all sorts of gremlins 

 

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Thanks for the continued help. 

Steve Q - Will definitely look at the gearbox oil change. 

Envy - Also found coolant is on minimum despite being topped up at the last service. 

Just trying to arrange cost effective transport to get it to the ramp/garage, seems most vehicle movers can only deal with cars up to 1500kg. Best quote so far for a 6 mile trip is £102. Although if this fixes it I won't care. 

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No coolant at the connector and no sign of water ingress either 😔

I saw a slightly different problem sighted a broken ABS sensor as the culprit. 

Could that cause what I am seeing? 

Open to other suggestions as well. 🙏

 

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