2016 GL350 P0404/P0405
 

I searched threads and can't seem to find what I'm dealing with anywhere.... Sorry if this is a duplicate. Beers on me....

2016 GL 350, 95k miles with zero issues.... Until now.....

CEL came on while driving around town, suddenly started "lagging" when slowly touching the gas... was sluggish, and once its warmed up, it didn't want to upshift, even using the paddles. P0404/P0405 also popped up. I turned it off and restarted it and no shift issues, but still sluggish.
While looking up OBD data, noticed my B1S1 showed 0.0 volts.
Thought maybe a bad O2 Sensor, so i replaced it and cleared the codes. Took on highway and noticed the "sluggish" was still there when I touched the gas, but it cruised smoothly though. After 30 minutes, starting driving back in town and the same symptoms mentioned earlier returned.

Lots of digging and thinking it's EGR-related, Changeover Valve? I saw a brief mention of this component on a thread that someone mentioned it impacted shifting....

Lots of sagely folks here and hoping for your help. Thanks!

If it’s a ‘16 you should post this in the x166 forum. This is for the older x164 generation.