99 SSE turns off while driving

[SgtPepper23]

Hey everyone,

i've had my Bonneville for just under a year now, only recently did this problem come about. It turns off while I'm driving, giving no indication that its going to happen, and it has happened both while the vehicle has just started running, or has been going for a while. When this occurs, everything on the instrument panel turns off, then right back on, usually. There have been a couple of times when this happened that it didn't turn right back on, and I worsened a bit of LA traffic... It is rather random when this happens, I have not been duplicate it at will. I've replaced the Mass Airflow Sensor, the Idle Air Control Motor, and cleaned out the Throttle Body (i don't think the previous owner had cleaned that out, it was so bad...) I've taken it to a trusted mechanic, he plugged in his OBDII computer and found no problem codes, even right after an unexpected shutdown.

I've looked at other similar issues that have occurred to other owners (thanks in large part to this community) and have read that it might be the Crankshaft sensor. That sensor I would not be able to replace myself, needing me to take it to the mechanic. How can i be sure that that is the sensor that is failing or needs replacing?

I'd appreciate any help that you guys can give me, and if more description is needed, I'd be happy to give more detail, though hopefully its enough to point us in the right direction!

[Oldman]

I had this happen a few times and after replacing a lot of parts unnecessarily, I found a bad connection at the ECM. It's under the coils, and there's a large plug with lots of wires and an 8mm bolt in the center that holds the plug in. Someone had over-tightened the bolt and cracked the plug and the center wires were held in, but the ones on the end were working loose. It would shut off while driving and usually would crank right back up again. Sometimes, it would take a long time to crank up. I'd loosen that bolt and take the plug out and clean all the contacts and hook it back up.
Good luck!!

[SgtPepper23]

Thanks! Is this something that can be done myself (i'm fairly proficient at repairing things) or should i take this to the mechanic again? If its something doable by a DIYer, where can I find a) the replacement parts (if needed, and b) a diagram of the area that needs attention.
I really appreciate your help! Can't wait to get my ride running smoothly again!

[96 SSEi]

hi, sounds to me like an electrical issue - please check battery cables, ecm - under coils for wire damage and pcm - near airbox for damaged wires....thanks

[SSEBonne4evr]

I had this happen a few times and after replacing a lot of parts unnecessarily, I found a bad connection at the ECM. It's under the coils, and there's a large plug with lots of wires and an 8mm bolt in the center that holds the plug in. Someone had over-tightened the bolt and cracked the plug and the center wires were held in, but the ones on the end were working loose. It would shut off while driving and usually would crank right back up again. Sometimes, it would take a long time to crank up. I'd loosen that bolt and take the plug out and clean all the contacts and hook it back up.
Good luck!!

X2 This is what it was for me, The ICM connector under the coils.
Because you dash is going dead, I suspect a bad battery connector, or ground bus
under the interior carpet. (search on here).