Instrument cluster failure- turn signal indicator and nav dead - K-bus fault?

[swissrock]

In my 2004 3.0d, several warning lights in the instrument cluster suddenly stopped working (turn signal indicator, high beam) as well as the PDC and navigation/radio, but the exterior turn signals on the vehicle still work.

At first I disconnected the battery, and after a few minutes everything was OK again. Then I read out the faults with Rheingold:

005F5B DSC: instrument cluster internal
005EB1 DSC: steering angle sensor supply

A few minutes later the fault pattern reappeared while driving, and the faults can no longer be read with Rheingold as long as the fault is present.

Then I read the faults directly in the instrument cluster with INPA:

• I-bus: short circuit to ground
• Light control module EEPROM fault: invalid operating range

After that, I swapped both the light control module and the instrument cluster for another one, but the same faults remained.

Even when the LCM is removed completely, these two faults keep coming back.

I now assume that there is an I-bus fault, which is probably caused either by a control unit or by a defective cable.

I have already disconnected various control units, cleared the faults, and read them out again, but the I-bus and light module faults are still present.

At the moment I’m a bit desperate because I no longer have an idea how to narrow down the problem further.


This does not seem to be a typical issue — what is the best way to proceed from here?