hi. can anyone help. i have a 2012 s550 with a auxiliary battery malfunction. i replaced the battery under the dash with a aftermarket one, it took a few days of driving and the light went off. after 2 months the light came on again. i purchased a genuine battery from fcp euro. the error comes on every start. sent the battery back and got a new replacement, same thing. the sam can be turn on with a scan tool to charge the auxiliary battery. the auxilary is at 13v. there is a code from the sam - auxiliary battery circuit open or not installed. what could be wrong? thanks