nomead

The Car:
2008 535i 6MT with 7/07 production date. Bone stock, no mods whatsoever.

Problem:
As it sits in my garage, the starter will crank once and stop trying.

History:
Without giving all the sordid details that led me to this point, I was driving down the highway and battery light popped up. A few seconds later, radio\iDrive, dash lights, climate control, really just about everything except headlights and tails went out. A few seconds later, accelerator did nothing so I pulled over and had the car towed home.



Steps taken:

• Replaced grounding strap using BMW OEM part in factory location. Confirmed 12V using various points on engine as ground, all showed 12.4V with 12.4V read across the battery terminals. Charged to read 12.6V but after some testing settles at 12.4V. Less than a perfect battery, but should work...please read on.
• Disconnected IBS from negative terminal on battery – same issue.
• Jumped starter solenoid to +12V – starter cranks over continuously.
• Tried using both key fobs – neither will crank starter more than once.
• Bump started car – Car started, runs and drives fine

Since I know it runs, I threw in a momentary switch to jump +12V to the starter solenoid, this works to start the car and I can drive it just fine. I understand the Car Access System (CAS) is sending unit to the starter solenoid, and understand this car has CAS3.

Is anyone able to recommend what steps should/can be taken to diagnose further? I read all I could find on CAS and understand it uses encrypted comms to the DME, and replacement would need to be a virgin unit to synchronize, but I don't want to throw parts at the problem hoping it fixes it.

I am afraid that the car losing the engine ground strap caused damage to the DME or CAS, but looking for a way to confirm/disprove that as the culprit. I do have another 08 535XI, but can't swap due to the VIN being passed to the DME.

BTW - BMW chose what must be the worst possible location for the engine strap on the E60, and I understand this is a common place for most of their cars.

NoQuarter

I would not think you could bump start the car and drive normally if something was wrong with the CAS or DME.

Weird problem to troubleshoot for sure.

Have you checked for any error codes?

nomead

[QUOTE=NoQuarter;1593313
Have you checked for any error codes?[/QUOTE]

Thanks for the reply. I did check and forgot to include. Immediately after losing the ground strap and towing home, I noted three codes,

• P1407 - Tank Fill Level Right Signal
• P1408 - Tank Fill Level Left Signal
• P3284 - not clear what this is...

Communication to DME worked, and after clearing and trying to start, no codes appeared.

Also worth mentioning that everything else seems to work, key is recognized and allows starting (though starter only tries one crank, remote door lock/unlock and trunk release all work, as does trunk release and panic mode.

NoQuarter

See what voltage is at the starter terminals when it cranks just the one time while holding down the start button.

JuniorB

There is a communication issue between the starter and the start button.

nomead

Been a while since I followed up, my apologies for that. A lot of travel for work, then a change in jobs, new apartment, blah blah blah.

Wanted to close up this thread. The fix was a replacement CAS. The root issue was caused by the engine grounding strap, which was no longer functioning and the auxiliary ground wasn't doing a good enough job. OEM ground strap replaced, new CAS with keys reprogrammed, and $1,300 later, it's running like a champ. The CAS blew a capacitor as it couldn't ground (that's the running theory anyway). The CAS sends 12V signal to the starter solenoid and it was terminating after a second or two because it was fried. The unit I ordered was supposed to have my keys preprogrammed, but they didn't work so a coder had to be called in reprogram, and updated the all the car software while he was in it.

Thanks for all who replied!