My E300TD felt sluggish yesterday and eventually, the CEL came on. I read the code and it's P0243, turbo wastegate solenoid. The turbo doesn't seem to be running at all as MAP reads 1 bar even when I accelerate.

What should I try first to fix this?

I tried swapping the EGR and waste gate actuator transducers and it didn't work. I noticed some of the hose connecting the waste gate actuator to the turbo looks worn, so I'll try to replace it and see if it makes any difference.

Inspect rubber hoses coming off each end of intercooler

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Jim

I solved it! A black vacuum hose slipped off the switchover valve near the fusebox. When I shut the car off I heard an air leak noise coming from that area, and I found it there, disconnected.