As is typical at our house on Sundays, we have to rearrange the order in which our cars are parked in the driveway based on who needs to leave the house first, second, and third on Monday morning. I noticed that when I started my car to move it (it had not been run since last Friday), my cooling fan kicked on and was running on high. Then came the MIL (malfunction indicator lamp [a.k.a., CEL, check engine light]). My A/C was not turned on (which, in most cars, commands the cooling fan on), and the ambient air temp was in the mid-60's (maybe low 70's) ºF. I immediately suspected what the problem might be, and it appears that I was correct. Code is a P0118 which is "coolant temperature sensor circuit high."

Live data said that coolant temp was -40 ºC (that is implausible, of course). So, either I have a bad sensor or a wiring problem. I inspected the wires, which are all on top and easy to access in my car, believe it or not. Noting apparent there, so I suspect it is the sensor itself. I will ohm it out tomorrow to confirm the diagnosis.

If it's the sensor (which I am all but certain it is), then I'll be making a run to the local Napper to get a replacement. If I have time, I will bring you along for the work (on my YT channel). Looks pretty simple. Disconnect the wiring harness; remove the retainer clip; the old sensor pops out of the housing, and the new one goes in; replace the retainer; plug harness back into the sensor. Easy peasy, right? Sure, but remember that it's an old car, and if that plastic retaining clip breaks, I am not sure I can get a new one, in which case I may need to get creative with Zip ties. Let's hope not.