Car wont start !!! Please help urgent.
 

So I connected VCDS to see why my adaptive cruise control warning was on. It suggested a voltage issue. I looked at the fuses.

Whilst I was looking I saw two connectors (one in each fuse box) and disconnected them to see what they were. They look to be power distribution of sorts. Plugged them back in, got loads of errors.

Since that, car wont start. Getting 05650 - Engine Control Module Incorrectly Coded amongst others. I Can clear them, they go away but come back.

With the key in my hand, car turns over, fires and then dies immediately.

With the key in the ignition, car turns over but never fires.

Clearly its not happy that Ive disconnected. The key works, locks / unlocks. On a BMW this would have been an issue where the 'Key Reader' and the ECU needed to be matched.

How do I do this on the A8? I can see some coding options in Access module but I dont know how to do this.

My car is stranded in my driveway, I cant get my wife's car out. We have an appointment in a while but that can be missed, but wont be able to get to work tomorrow.

Anyone help please?

Thanks

Just try leaving the battery disconnected while you do something else and when you reconnect, hopefully everything will boot back up in the correct order.

Ok, its fixed.

What it looks like is that I had enabled the wrong type of cruise control module. Should probably stay away from the coding stuff, didnt realise it wasnt just a login to 'see' but actually changes something.

Now that the car is running again, I still have the ACC not available error (which is the reason I started to look around). Im getting a 0V error based on codes read.

Fuse looks ok. Where is the ACC module and does anyone have a part number? I'm getting two different part numbers which dont seem to be correct.

Not sure how difficult it is to replace / recode this part ... ?

The ACC module (distance control unit J428) is integrated into the radar (distance control sender G259) as one unit behind the bumper. What is the actual fault logged in 13-Distance Control, just the voltage reading?

Can VCDS connect to 13-Dist. Control? It could be a damaged wire to the Radar? My first investigation would be to test the wiring.

You'll have to remove the bumper to access the connector for the radar; with ignition on bridge pins 1 & 12 (T31 & T15) on the plug (NOT RADAR!) with a multimeter - note if there is current by measuring the voltage.

If the above is good now drop the glove box for the connection to the CAN gateway. Create a closed circuit by attaching a multimeter to Pin 2 at radar plug and Pin 13 at gateway plug, this is testing CAN-H. If a closed circuit then CAN-H is good. Now create a closed circuit by attaching a multimeter to Pin 4 at radar and Pin 26 at gateway, this is testing CAN-L.

If all these tests are positive then the wiring is good. Next thing is to test the radar, I can do this on my test bench setup. Let us know how you get on with the above first.

Just to be clear for anyone facing similar in future. Did Snapdragon's advice work? Or was there something else that sorted it?

I've had something similar with a key related error code - cleared an error and the immobiliser was cutting in whenever you tried to start the car.

I locked the car up and let it go to 'sleep' for an hour - went back out and it started immediately :rolleyes:

No, sorry, it was teh wrong 'access' code I had put in at the coding box of Engine which basically told my car it has the standard Cruise Control module. When I fixed this, it started.

Thanks. The error was '00446 - Function Limitation due to Under-Voltage. 002 Lower Limited Exceeded.' The pic I have doesnt show but I recall it says 0V lower down.

Yes, the module seems to be able to be 'read' as its giving codes or something is.