rheplo

Can anyone help diagnose this issue? It is the second time it has happened within the last couple months. VCDS log is attached. Thanks in advance!

maxandtara

Is your battery new ? if new
Your Voltage management may be defective..

The voltage regulator is in the alternator. Battery management is the module the battery is attached to.

The Car battery indicator is useless.

Personally, for the sensitive electronics power is drawn from the battery (stable power source).

Some cars opted to have a 2 battery system to solve this issue. Audi opted for a huge battery for the A8.

From the advice of most people here replace your battery if it is more than 5 years old.
The battery I had was more than 5 year old, it can still start my car, and the battery indicator said 100%.
From Personal experience I spent hours hunting down electronic gremlins. Nothing made sense.
After replacing the battery, the issue I was trying to fix just went away.

If your issue is either the battery or the voltage mgt system. It is a cheap fix for the A8.

If not good luck!

dart

rheplo

I replaced the battery recently along with the fan belt. Is it possible that the voltage issue is related to over tensioning the fan belt?

Regardless, I’m more concerned with the MIL illuminating due to the SAI

dvs_dave

The bank 1 Secondary Air Injection combi valve has failed, or the vacuum line driving it is leaking. Relatively easy fix on the V10’s as both combi valves are adjacent to the SAI pump under the right side air box.

rheplo

Thank you both for your help!