Fixed Lambda Redaing of 20
 

My 1988 300SE has a fixed duty cycle lambda reading of 20. I've searched the archives but can't find anyone who asked this before. What does this reading indicate? The O2 and coolant temp sensors have been changed but I'm still reading a fixed 20 and still running rich.

The CD says "Full load switch incorrectly connected or faulty."

Of course I have to ask...
 

What and where is the full load switch? That is something I've never read or seen in any post.

It's on the front outside of the air sensor assembly just above the intake manifold. I think it is black plastic and it has wiring that runs to a connector just to the outside of the idle valve. It's function is to tell the brain whether the system is at full throttle or idle or something in between. I believe that its main function is so that the EHA can go to "full enrich" at full throttle.