About two weeks ago I started my car up and had the CEL come on. I finally decided to order the Auterra scan tool as the car was running fine. Well it arrived and when I did the check I got a P0116 "Engine coolant temperature circuit range/performance problem". After I reset it I drove down the road and everything was fine for about 6 or 8 hours and then it came back. The cool part was that this time I was playing with the new toy and actually had it recording the readings from three sensors when it occurred. The sensors were "Engine coolant temp." "engine rpm" and the "vehicle speed". What I see is that the temp. appears to remain around 216 to 220 deg. F most of the way with one sudden unexplained drop from 216 to 196 in a period of less than a minute then immediately back up to 216. Am I looking at a sensor going bad, a short somewhere or what?

The speed and rpm do not seem to factor in anyway with the drop in temp. However later on I watched when the light came on yet again and once again the temp was low on the dash gauge only to jump back up. I reset it and it has stayed off but I'm sure it will reappear. Anyone have ay ideas?




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~William~ 1985 240 DL - 357,000 & 1998 V90 - 99,000