Need your help. 2009 Mercedes Benz clk 350 88,452 miles 1 owner. was up at 3 am, couldn't sleep. Received a call from friends co worker. On the way to work her car went completely dark, everything shut down, it Started right back up and it was fine, 5 minutes later it happened again. She started it right back up and she made it to her job but car went into limp 2 min from destination. I go there and look over her car,. I cannot find anything wrong, I tested battery and alternator, everything checks out. My expensive scan tool cannot find anything wrong. I did a real deep dive and spent 85 mins carefully looking over data. What do you guys think I should check. I feel there might be a short with battery cable. Also I'm thinking it might be multiple SAMS failing. Possibly a computer problem.
My guess is the computer issue, since she could start the car after it shut down, there should be some issues there. Maybe take it to a Mercedes mechanic to find out.
When I had a very similar issue with my Audi, it was the positive battery wire (or its connector, to be more precise) shorting very slightly against the chassis and causing ECU outages.
I told her she might have to bring it to Mercedes. I'm going to look it over again now it's light out and not snowing. I'll check the positive to make sure it isn't shorting.
I found out what's wrong, her battery is bad. I hooked up a digital battery analyzer and a battery/alternator tester in the 12v socket. I started car and after 5 min both went to 0 and car died. Few moments later they both read 13.3 v. I removed battery from car hooked up analyzer, I bumped battery and it went to 0v then back up to 12.9 v. I did it again a second time and same thing happened. I got a new battery installed in her car and everything seems good now. I told her to still be alert and to report back later today.