Hey all, a couple of weeks ago my wife's C200 started displaying this error every 5 seconds on the central display in the instrument cluster. I sourced a replacement part (don't get me started on the attitude of the local MB dealership's parts department when I asked for a current part number), and even after fitting this part and also disconnecting the negative terminal on the battery for 15 minutes, I am still getting the Auxiliary Battery Malfunction error. Is there anything I can do to clear this myself, and are there any other troubleshooting steps I should take in an attempt to resolve the error or am I relegated to heading to a mechanic to have this investigated?

PS, I cracked open the original voltage converter and there's no visible burns on the PCB or swelling of the capacitors.

Thanks in advance for your help everyone.

When I pulled mine apart the capacitors had burst and leaked onto the circuit board, fitting a replacement part solved the problem. Yours sounds like some other issue, maybe check the connector plug has all the connecters in place

So I've checked everything on the voltage converter which looks fine, I also checked the battery which was sitting at 12.1 volts resting voltage so I have replaced, and also checked the trunk fuse that can cause this and all looks fine.

Has anyone got any tips as to what else this could be?

I've found a local mechanic who was happy to read and clear codes for me. Had a few but the one that has stuck around is U11A300 "communication with control module multifunctional camera has a malfunction", and the Auxiliary Battery Malfunction error is still appearing.