gcracka

I replaced my battery today in my '08 Q7 and now the mmi won't work. No accent lights are on in the mmi buttons. No backup camera when in reverse. it will attempt to start up if you press the on/off/volume ****, and the startup mmi screen appears but then goes back off again. The cd changer comes alive if you press the load button, but I don't have a cd to test it out with. I have read that the battery needs to be coded, but I haven't seen any mention of needing to reset the mmi after the battery change. I just had an oem trailer hitch put on the day before by a local euro car specialist and I am wondering if the battery drain is because of that, but may just be coincidence. I am about to pull a boat 3.5 hrs tomorrow and I would really like the use of my mmi for this trip. Any help would be appreciated.

Thanks,
Graham

smith2010Q7

I hate to say this, but you are correct. The shop splice into the wire harness that controls all the components that do not work. What it did is it cause the ECM systems to not go into sleep mode which tells me they splice into the power wire harness. Which cause your battery to drain. Also need to scan for which Module they have fry. Hope that the fuse fry first instead of the module.
Look at your right luggage fuse panel for any blown fuses. also your wire harness is in that location and see how they have done the work.
Have to fix the battery drain problem if you can before you leave, hate to see you on the side of the road.
The battery coding is about to tell the ECM that you installed a new battery so the ECM can tell the voltage regulator us less volts to charge your battery.
You are going to see a lot of battery codes, so clear everything and run the car to bring up the good codes.

Your towing control module wire harness too the list below.
J104 - ABS Control Module
J345 - Towing Recognition Control Module
J393 - Comfort System Central Control Module See
J508 - Brake Light Disable Relay See

see chart for fuses

Q7 towing fuses.pdf

gcracka

Thanks for the reply smith2010Q7. The mmi did work after they did the tow hitch install, and it wasn't until the battery was replaced yesterday that the mmi stopped. I have a simple Bosch scan tool will that register the codes and allow me to clear them?