I finally got around to changing out the valve cover gaskets, and tried to start the car after doing the right side. The engine turns over but will not start.

4 Motor Electronics Codes:

P3675 Component "M16/4 (Rear throttle valve actuator)" has a mechanical fault. The throttle valve adaptation has a malfunction.
P0224 Adaptation of the idle position of the throttle valve actuator was not performed.
P0868 The control unit has a malfunction.
P1108 The power supply at the input of the control unit "composition engine" has a malfunction.

Now I wonder if I leaned on something, or did something wrong (can't imagine what that could be) or if this is all coincidental, meaning, it was gonna happen anyway, but just coincidentally happened when I did the work (?!?)

After reading the codes from the earlier start attempt, I found additional codes:

P1347 Mass air flow sensor 1 has a short circuit to ground
P3690 Component "B2/6 (Left hot film mass air flow sensor)" has a short circuit to ground

Now I'm REALLY starting to think I did something to disrupt the MAF circuits when I cleaned both air filters. Hmmm...

Sounds like something is pinched or unpluged. Back track every step and find it.

I'm doing that now. I'm hoping it's something close to what's described in the related thread below.



I did find this... researching the part now- I believe it's the valve actuator??

Problem solved, and it does seem to be coincidental: Fuse #43 in the engine compartment. It's a 15 AMP fuse that caused all those codes. Changed it out and the car started immediately.

I don't have the fuse listing for your E63 but for all previous W211 gasoline engines that fuse is listed as providing power to the motor electronics; for the diesel engine W211 version that fuse powers the CDI plus front SAM and, in two engine versions, the rear SAM as well.