My '04 R53 has been completely reliable for its entire life. Now, suddenly, I have an occasional electrical gremlin that has me concerned. In the last couple of weeks, occasionally, I will be idling at a red light when the entire electrical system goes out just for a second. The engine quits and the lights go out but everything comes back on just as quick as it went out. I don't know where to start looking because it is infrequent, can't be reproduced in the driveway, and always fixes itself. I'm going to check codes to see if anything new pops up (check engine light is always on because cats are temporarily removed). Where should I start looking for problems?

 

Loose and/or corroded wires is where I would start looking. Fuses, chassis connections and crimped wires where they would be exposed to outside elements is where I'd go first.

 

^^ +1 ^^

Start with the connections; Battery, Chassis Grounds, ECM connector ...

Also have your battery Load tested.

Best of luck tracking down the glitch ...

Motor On!

 

I have the same problem, but only with the clock/radio. Only when idle dips to 750RPM or so. Engine hasn't cut out...and its winter, so I haven't had the chance to review alternator connections. Battery is new. I'll respond back if I find out what it is.

 

Check how your regulator is functioning as well.