I have repeated Check Engine Light codes for the coolant temperature sensor. Other than the CEL, the car is running fine.

Last year at this time I had the same problem and replaced the sensor. It has been good until now, but I can't imagine that it is the sensor is bad again.

I am not sure if 100+ degree weather or coolant type could contribute to this...that would be bizarre. So I wanted to see if there were any less bizarre idea.

If it isn't running too rich, I wouldn't think the sensor is really bad. I would reset the codes and see if and more importantly when it comes back. Maybe there is a particular condition (big bump or something) that sets it.

I'm thinking wiring.
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Andy in St. Paul. '89 244 153K mi, '91 745 Regina 202K, '88 244 184K

Have you considered a sticky thermostat yet? Often times depending upon the age and mileage of the car I will sell them as a kit, T/stat and an ECT sensor.

Mark

Thermostat and operating temperature are fine. I'm seeing the 1-2-3 code indicating a problem with the temperature sensor or signal.

It could be as simple as another bad sensor. I replace them often enough that it would not suprise me. Thermostats are cheap and can cause a 123 code, I would hang a new thermostat, either a factory Volvo one or a Wahler, and replace the sensor again.

Mark