Sorry for double posting but found out that if you calculate a NEW SVT with 674 instead of 676.
AMPH is expected. This means that a new ECU is expected when coding 674.
See screenshot 1. (Ignore missing AAG, this SVT_soll includes 23 compared to SVT_ist without 235)
This is not the case with just HiFi which probably means that it could be that the HiFi Amplifier is NOT on the canbus, where this missing link lies is unknown. Is it due missing cables in the connector to R4 resistor or is it in the amplifier itself...
Attached wire diagrams. I don't know which production year you have but it seems there are 3 different versions of the R4 wire diagrams.
Unsure what the 'minor' differences are but TIS list but looks like
I attached 2017/07+ say if you need other version
Wiring Diagram (SSP) Body CAN4 bus connection
- -2016/06
- 2016/07 - 2017/06
- 2017/07+