Troubleshooting Engine & Electric Cut Off? - The Unofficial BMW M5 Messageboard (m5board.com)

FitForFives · 28th July 2008, 11:59

Hello everyone. I am a fairly recent member in need of help.

I was driving the E39 today and when I stopped at an intersection the electronics flashed quickly and then the motor and electric cut out. I got out of the car, waved the traffic to pass (no hazard lights) and the cabin lights popped on. The engine started and I drove away with no further problems.

About a month earlier I ran into the store and left my girlfriend in the car. When I came out the engine wouldn't start and there was no electric. I got out of the car hit the keyless entry, after a minute i noticed the cabin lights turn on. Stupidly I supposed it might have something to do with the security system which it clearly does not. It happened another time when I was parked and the engine was running. Same result, a minute later the electric kicked back on. Finally the day before yesterday coming off of a highway going about 40 MPH the lights flickered and I thought the engine was going to go, but it did not and I finished the drive without incident.

Clearly I was foolish not to address this problem earlier. The next time I drive the E39 will be to the mechanic. I would appreciate any information or similar experiences.

Alin10123 · 28th July 2008, 12:57

Sounds electrical. Check the easy stuff first. How is your battery?

SSense · 28th July 2008, 12:58

The wires on the battery could be loose , thats one reason why engine could go off. Dont depend on my reply, wait for our other M5 experts to post their replies too, im sure you'll get a solution, dont worry.

kees · 28th July 2008, 14:21

Start with the cheap stuff:
- check the battery connections are tight and clean
- replace the battery

m5 deamon · 28th July 2008, 16:24

i would ck your connections to battery and the connections on the power block on the passenger right side behind the compartment in the trunk from there i would ck all your grounds

DouglasABaker · 28th July 2008, 16:49

Loose battery connections will not stop an engine from running, but that and a faulty Unloader Relay are about the only thing that will cause you to lose all power to the car. A faulty unloader relay could also cause your vehicle to lose all power while driving (and cut out the engine in the process).

For reference, the unloader relay is how BMW turns off all the electrics when you start the car. I would posit that yours is going bad and needs to be replaced ASAP - all relays go bad over time (did you know the circuit breakers in your house need to be replaced about every 20 years or so?), so don't let it give you any pause about the roadworthiness of your beast...

d-

m5 deamon · 28th July 2008, 18:05

doug i was waiting for him to ck what i wrote and i was going to state the samething you did about the main realy

DouglasABaker · 28th July 2008, 23:45

Quote:

Originally Posted by m5 deamon

doug i was waiting for him to ck what i wrote and i was going to state the samething you did about the main realy

Great minds think alike

(written as I sit here stuck at LGA waiting for the next shuttle to Boston in 2 freakin' hours...)

d-

FitForFives · 28th July 2008, 23:50

Thanks for all of the suggestions. Just brought it to the mechanic, so hopefully it works out.

FitForFives · 30th July 2008, 23:01

Got my beast back form the mechanic. They replaced the ignition switch. They said that this is a common problem in E39, E46, and other models from the 2000s. So far so good, but I guess only time will tell.