My ASS is Fixed, BMW Auto Start Stop Resolved

Josh's 2012 BMW 328i in Service Bay

If you’ve been following me over the past few months you’ll recall I purchased a CPO’d BMW 328i back on May 20th only to have it spend every day since at the dealership while they attempt to fix the Auto Start Stop (known to the technicians as MSA) feature. The ASS is a function that automatically turns the engine off when the car comes to a stop. The idea is to conserve fuel. The engine automatically restarts at the appropriate time to take off. Not exactly seamless, but it works (on my loaner car).

None of us could believe such a thing would take so long to be resolved by a BMW dealer, but it has. And as of now I’m happy to announce that BMW tells me it’s been fixed. Granted I haven’t driven my car yet so I can’t confirm with my own eyes but I’m going to take their word for it and reveal the culprit. It may surprise you.

BMW Start Stop Button

The BMW Auto-Start-Stop (Internally known as MSA) Failure Has Been Resolved.

What was it? A silly ground wire. There is a ground wire that goes from the chassis to the transmission. It’s supposed to be there. For reasons unknown, at some point under the previous ownership, the tranny side of the ground cable was relocated to the exhaust.

How does that ground cable effect ASS? When the engine is cold, the cable provided the right voltage to allow other systems to operate. After the engine warmed up the voltage became out of range and caused other parts, namely the starter, to not operate properly. Reattaching the ground cable to the transmission seemed to fix the problem. Or so claims my service advisor.

So did it fix it? I can’t confirm. My car remains at the shop while the timing chain is replaced with updated parts from BMW. Could have my car back as early as this time next week. Stay tuned.