A momentary overvolt can only mean voltage regulator. Once that is intemittent bad, you can expect all modules to go haywire.

Trifecta is often the first indication even before batt light.

You could possibly test by disconnecting the alternator after starting but that's a pretty high level test.

With your scanner can you point vBat? If so do so, and if the voltage ever goes over 14 or under 13 vReg is shot.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)