dvs_dave

You need to get to the bottom of those system wide low voltages before doing too much more. Readings in the 10v range will cause errors.

As there’s a likelihood of water damage/corrosion, you need to have dig around and check for corroded grounds etc. and clean them up. This would cause system wide low voltage issues.

What voltage is the alternator putting out? (Measuring block in battery regulator module)

What’s the voltage at the battery terminals? Engine on and off. Check the cigarette lighter too, see what that’s doing. Definitely something not right. Is the +ve battery cable warm? Recently someone on here with an S8 was having voltage problems and it turned out to be a bad battery terminal cable.

91quattro

Agree - corroded contacts, oxidation, wiring - something is dropping that voltage, especially since you have a new battery. You shouldn't be seeing 10.795 volts anywhere at this point. Audis can do strange things when the voltage is on the borderline, like in this case. I'd get out my voltmeter and start measuring voltage in the suspect area and examining electrical contacts, starting with those ECUs.

scotty11

Is there any reason I shouldn't replace my ecms now? I'll have the used pair in hand shortly.

Obviously I still need to clear those drains, and track down this electrical issue.

scotty11

I just had the ECMs replaced at the dealership and the lights are gone.

I haven't run vcds yet but will report back if anything weird comes up.

Thanks again everyone for the help.