Sorry if I'm stating the obvious, but a dead battery will chuck up many faults.. have you tried a new battery front/ rear... red battery warning suggests its dead. when my consumer battery went dead.. all faults were related to it.
I'll also repeat the obvious, the R230 is infamous for flattening its consumer battery (but not its starter battery), when left unattended for 4+ weeks, especially if the battery wasn't fully charged when it was parked up. SL's are often used as 2nd car runabouts for weekend or summer use, so seldom get a chance to charge that consumer battery "on a run."
Once that battery flattens, it can kick off a variety of false error messages across a range of sensors. An electrician knows how to check and dismiss false warnings. Dodgy error messages are endemic across all modern vehicle electronics - not just the R230, nor MB. Those warnings are there for good reason, but they can lead you down dozens of false trails.
The easiest, and ecologic, is to stick the consumer battery on a battery conditioner, which is different to a "charger," and charge / condition the thing back up again, rather than replacing the battery.
But, and here I get to my real point, if you've got electrical problems, use a car electrician. They're cheap, don't have MB main dealer overheads, and know more about electrics than any willing amateur will ever be able to take in.
