Marty,

I had forgotton about that earlier thread started by Merkey. I do have some differences though. When I put black probe into #3 and red probe into #2 (as in his second picture), I get a 30.0% reading. My MB WIS does spec a KOEO30% reading with coolant temp <70 deg, and 70% >80 deg. This is for a Federal/CA car as of 9/89.

I therefore attribute this baseline difference to him having an '88 and me a '90.