A8 2.8 Sport - lost 5th gear and Tip,
Discussion
My A8 has gone into default mode on the box. A ZF specialist has charged me £300 to check diagnostics and swap out a sensor - made no difference so they swapped it back. The ECU still reports no signal from the gear sensor. They wanted to change the ECU next 
.
I get all the gear positions lit up on the dash, gearbox does its own thing irrespective of gear postion (apart from N and R), the tiptronic doesn't work, and it won't go up into 5th. I beleive this is the default mode.
The car is still driveable, just a bit busy at motorway speeds.
I reckon it is probably a wiring fault. Anyone have any ideas where the likely connectors are, or where I can get hold of a wiring schematic for the A8?
>> Edited by victormeldrew on Saturday 1st October 17:37
. I get all the gear positions lit up on the dash, gearbox does its own thing irrespective of gear postion (apart from N and R), the tiptronic doesn't work, and it won't go up into 5th. I beleive this is the default mode.
The car is still driveable, just a bit busy at motorway speeds.
I reckon it is probably a wiring fault. Anyone have any ideas where the likely connectors are, or where I can get hold of a wiring schematic for the A8?
>> Edited by victormeldrew on Saturday 1st October 17:37
Mr Meldrew
You can buy an A8 Service Manual from www.bentleypublishers.com/product.htm?code=ad25 in the US. This is obviously for a LHD car, but since it is a very low volume car I suspect that a lot will be the same/similar.
Audi UK will not sell you a service manual/wiring diagram, I asked when I was having intermittent electrical problems.
In the end the problem was diagnosed as needing a new ECU so I'm afraid the Audi went as the ECU price I was quoted was just palin scary (and about 25% of what myt car was worth at the time). You might be able to source one from an upmarket breakers though.
It may be that you have a genuine problem and the ECU has gone into this mode to protect something, the electricals and sensors are a maze on an A8. The A8 is a complex car and a lot of even quite monor signals are routed/controlled by the ECU.
Personally my life has been much easier since the A8 was sold, I've done 100,000 miles in a Saab 9-5 with a normal servicing and a couple of minor faults that were fixed under warranty. And I've just mamaged to get a further 3 years unlimited mileage warranty cover (inc Turbo) for £600! The A8 is a great car when it works, but when it doesn't its a nightmare.
Best of luck in solving your problem
davidy
>> Edited by davidy on Saturday 1st October 17:45
You can buy an A8 Service Manual from www.bentleypublishers.com/product.htm?code=ad25 in the US. This is obviously for a LHD car, but since it is a very low volume car I suspect that a lot will be the same/similar.
Audi UK will not sell you a service manual/wiring diagram, I asked when I was having intermittent electrical problems.
In the end the problem was diagnosed as needing a new ECU so I'm afraid the Audi went as the ECU price I was quoted was just palin scary (and about 25% of what myt car was worth at the time). You might be able to source one from an upmarket breakers though.
It may be that you have a genuine problem and the ECU has gone into this mode to protect something, the electricals and sensors are a maze on an A8. The A8 is a complex car and a lot of even quite monor signals are routed/controlled by the ECU.
Personally my life has been much easier since the A8 was sold, I've done 100,000 miles in a Saab 9-5 with a normal servicing and a couple of minor faults that were fixed under warranty. And I've just mamaged to get a further 3 years unlimited mileage warranty cover (inc Turbo) for £600! The A8 is a great car when it works, but when it doesn't its a nightmare.
Best of luck in solving your problem
davidy
>> Edited by davidy on Saturday 1st October 17:45
Thats OK David.
I may have found the problem already. The main connector to the ECU does not fit correctly (there is a white ribbed seal around the plug which won't fit into the housing, so the plug isn't correctly seated and there are gaps. There are signs of moisture in the ECU box (which is supposed to be sealed) - like mildew on the labels for example.
More importantly for me one of the pins is badly corroded - lots of green residue. Why one pin in particular I'm not sure, must have been directly where there was water ingress past the faulty seal. So, quite possibly an explanation for the "no signal" error code the ECU was giving out.
I've cleaned it up, and done my best to get a good seal when putting it back. It hasn't cleared the problem, but I think the ECU needs to be reset. I've ordered a diagnostic lead and software so I can reset the error code myself rather than have to take it to a dealer.
Fingers crossed the problem will be sorted.
This is the only real problem I have had in six years of A8 ownership to be fair. It wouldn't stop me from getting another, its an awful lot of car if you get one at the right price.
I may have found the problem already. The main connector to the ECU does not fit correctly (there is a white ribbed seal around the plug which won't fit into the housing, so the plug isn't correctly seated and there are gaps. There are signs of moisture in the ECU box (which is supposed to be sealed) - like mildew on the labels for example.
More importantly for me one of the pins is badly corroded - lots of green residue. Why one pin in particular I'm not sure, must have been directly where there was water ingress past the faulty seal. So, quite possibly an explanation for the "no signal" error code the ECU was giving out.
I've cleaned it up, and done my best to get a good seal when putting it back. It hasn't cleared the problem, but I think the ECU needs to be reset. I've ordered a diagnostic lead and software so I can reset the error code myself rather than have to take it to a dealer.
Fingers crossed the problem will be sorted.
This is the only real problem I have had in six years of A8 ownership to be fair. It wouldn't stop me from getting another, its an awful lot of car if you get one at the right price.
they are Gassing Station | Audi, Seat, Skoda & VW | Top of Page | What's New | My Stuff