E46 M3 randomly shuts off while driving?

[Originalyokai]

E46 M3 randomly decided to shut off on the highway. Three times today out of the blue. It shuts off and then turns immediately back on like it cycled it's power. The sport mode turns off and no lights come on for CEL. really weird encounter although it's been somewhat cold in Colorado today was around 50f.

[bmwdirtracer]

crystal ball2.jpg

I'd start by replacing the crankshaft position sensor.

[MIKYZZ4]

According to my own similar experience, I would check for loose battery connections.

[shadowpuck]

Yup. Loose battery connections sounds good to me.
but. I’ll always throw a bet on the crystal ball. Hard to argue against that!!

[MarcoZandrini]

The first step in diagnosing a problem is to scan the engine computer (DME) for codes.

[bmwdirtracer]

I have known idiots who claimed to have changed the battery while the car was running. Loose battery connection will prevent the car from starting, and/or give a huge voltage spike to all the computers when the cable comes loose, but it won't, to the best of my knowledge, cause the engine to shut off, if the alternator works, unless the DME gets fried from the voltage spike. That said, I strongly advise against anyone trying, and I certainly think it's a great idea to check all primary ground and power connections.

Besides the crankshaft position sensor, another likely culprit for this scenario is the failure-prone ignition switch. Neither part is terribly expensive, and it's common that when either fails, it doesn't leave a code as evidence. These two would be my prime suspects.

[MarcoZandrini]

Chris, a loose battery cable will cause the engine to shut off. It happened to me. Luckily it was on a surface street and not on the highway. And luckily I was on the side of the street that was downhill so I could coast into an open parking spot!

[bmwdirtracer]

Thanks, Mark, I will certainly take your word for that.

[fiveoh143]

Ignition switch

[bmwdirtracer]

Interestingly, Mark, I had a customer in the shop today, with a towed-in E36. His ignition lock/switch failed when the car was running, and he couldn't shut the car off. So he disconnected the battery hot cable....and the car kept running. He finally got it to shut off by unbolting the main hot feed to the fuse box underhood.

It doesn't seem like the original poster is ever going to come back to tell us the results anyway.....

[328 Power 04]

Interestingly, Mark, I had a customer in the shop today, with a towed-in E36. His ignition lock/switch failed when the car was running, and he couldn't shut the car off. So he disconnected the battery hot cable....and the car kept running. He finally got it to shut off by unbolting the main hot feed to the fuse box underhood.

It doesn't seem like the original poster is ever going to come back to tell us the results anyway.....

This is how my old E36's radio was fried.