2017 GLS550 Turbo A Underboost CEL

[kevm14]

A lot of suspension bolts want to be very tight. In fact so tight that the alignment guy didn't tighten them on my E63 enough at my local shop (before I went to the dealer) and I had to tighten them myself because the lower control arm was moving under load and making an unsettling clunk. Then there is your wiper arm fiasco. So yeah, bolt torque.

[rpaoness]

Now refrigerant capacity - w/ rear AC and/or code 2U8.... hmm...

[rpaoness]

Went with 1050g since that seemed to be likely the right one. Test drive went ok other than I now have a heated 02, bank 2 pending code. I hope the connector and wires are ok and it just didn’t fully click in or something. I’ll check it out in the morning when the cat isn’t 900+deg.

[kevm14]

Wasn't there a sticker under the hood somewhere for refrigerant capacity? I'd also double check that it's r134a....

[rpaoness]

I had looked at a couple listings to make sure it's R134a - all indications are that year/model it still was. I also (potentially naively) assume they would change the quick connectors to something else for 1234yf or whatever.

It was just one of the O2 sensor plugs hadn't fully mated. Had to loosen the cat-to-manifold bolts and pull the cat-to-resonator clamps to rotate the cat enough to get my hand up there... stupid tight.

Fortunately I could leave one cat-to-manifold bolt in because landing/starting that first one with the floating flange on the cat where you can't reach was a huge PITA.

Seems to be all set - no new pending codes. Just permanent now O2 and boost, but hopefully those clear in a couple drive cycles. No CEL at least for now.

[rpaoness]

There's a blank spot on the radiator support plastic cover that I think is where the label was supposed to be. There's no sticker there now.

[kevm14]

Those can be ordered. In my case it was $16.

viewtopic.php?p=24690#p24690

There was a place in EPC to view the labels.

[kevm14]

How does it drive, specifically under boost and transitioning in and out of boost?

[rpaoness]

Idk - seems fine. Maybe more low end torque? I believe I hear some turbo whistle that I don’t think I heard before.

[kevm14]

There's a blank spot on the radiator support plastic cover that I think is where the label was supposed to be. There's no sticker there now.

Those can be ordered. In my case it was $16.

Here you go.

20260627_130237.jpg

https://www.mercedesbenzpartsshop.com/o ... 1665840238