OldAudiS8

Need help with this, I have a 2007 S8 that just stopped starting. I drove the car, and everything was good. 8 hours later no crank with the start button or the key. Then the dash display lights stopped working, then interior lights, now even the nav and info screen won't open. I have charged the battery and it's only a year or so old. Voltmeter says 12.6 with battery disconnected, I bought it from Audi. I have been checking for power at most of the circuits under the dash and footwell, trunk and fuses. My head is spinning, where dose the start and key get its power from? I replaced two relays on driver's knee bolster relay panel. I think they are 15 & 75? (both had power 12.3) Booth RT & LT footwell heater fuses were blown. There are some others that don't have power that are still good. Where do I get wiring diagram for the ignition switch and start button?

Right now, I have a no dash lights and no engine cranking to start. With the key or the start button. Info screen is opening, and the radio is working.
I don't hear and clicking from the starter relays.

Rob09A8

A8 Parts Forum D3 Manuals and SSP's

https://forum.a8parts.co.uk/showthread.php?t=9347

PDF's are numbered on the Left side.
Workshop manual Electrical PDF #23 Group 94- section 22 page 242
Also Pdf's #53 and # 54 are SSP's

https://forum.a8parts.co.uk/showthread.php?t=9347

TSHong

Sounds like your steering lock cylinder is still engaged so your modules are not powering up. You will need to check your start authorization to see if you have a code. If you have a steering lock code, sometime it will not allow the lock cylinder to disengage and let you start your car. Try this procedure.

OldAudiS8

Thank you I will give it a try. I did forget to mention I had no communication with at the OBDII connector.
The video showed how to get around that issue. Fingers crossed that it works.
Thanks again for the info.

OldAudiS8

It didn't work, I have no communication with scan tool. I check the battery voltage it's 12.1 volts. Could the Alternator be the problem?

Rob09A8

There might be something here to be able to get in and scan it.

https://forums.ross-tech.com/index.php?threads/7092/

TSHong

Even with that voltage, you should be able to communicate with via obdII following the instructions. Your alternator recharges your battery and supplies electricity to your after the car has started so the ALT is not your issue withe the modules not powering up.

Rob09A8

Did you get to try this?
[That thread by aTOMic is an all time hoot by the way!!]

Bought a circuit tracer to "tone out" the +/- if necessary, but first I triple checked the fuses with a $5 Buss(man) fuse tester. You know, the yellow ones which last until the day before they're needed and then the batteries bloom into a magical garden of corrosion and oxidation. I had previously checked for continuity the fast way - multimeter set for diode/tone - and all was OK. This time, the little yellow savior found that fuse #24 (IIRC) - access and control module was open! Moreover, it was a 20A fuse in a 25A spec'd slot! Replaced it, the car started right up.

OldAudiS8

Okay I am Back. Still have no crank or dash lights.
My girl was driving the car the day is stopped starting. She said the EPC light came on while driving but everything was fine.
I have the driver's side opened up to get to the relays and pulled back the passenger's side carpet to get to those as well.
I have to start over because I lost track of where I was and what I have done.
The sunroof did leak a few years ago and that side got wet. I did pull the carpet and vacuumed out the water that day.
I don't think the box got wet and I have opened it and checked it out. Looks new inside.
Could the power control module have failed?
Would this cause the no crank no dash lights. Everything else in the car is working windows, seats, outside lights, power trunk.

dvs_dave

So it since started working again, and now it’s stopped working again?