I have the following issue. Getting the red battery icon randomly on my SL55 2002. Had it for 2 years now after winter storage every year, but it always went away after driving a while. Now it comes back every time after driving and sometimes right away after starting. Fault comes very randomly.
Car seems to shudder a bit on idle, but while driving no issues and runs fine (smells a bit rich on idle?) And another issue is that the IC loses power sometimes when turning key to 0 position and back to 2. Power to the engine components works at this point but cant turn the key to start when this happens. Remove key and everything works fine again. Not sure if these two are connected. EIZ was repaired last year.

- Batteries tested to be ok. Charging voltage on rear around 13.8V to 14.2V. Charging voltage on front battery around 14V also.
- Measured the 2 wires coming out of the alternator and the other one shows charging voltage and the other one varies from 3V to all the way upto 10V depending on RPM. Both tested 0OHM resistance so wires are ok.
- Getting a fault code B1828 Component K57 fault (or circuit 61). K57 relay is new from Mercedes, didn't fix the problem.
- Tester shows all charging voltages to be ~14V and key on engine off ~12V
- Voltage regulator is new

Does anyone have the SL55 ECU pinout so I could measure the values the ECU is getting. (not sure if ECU related tho)
Or what would you recommend I measure next? Need a new perspective on this on what to look for next before throwing new parts at it.

And does anyone know is the CAN-H and CAN-L supposed to have a resistance between them? Saw this question on the forum but that was never answered. Measured resistance on the ECU pins and got 120 ohms but from the blocks shows nothing.