Hello all, I'm fighting a crazy issue that is driving me nuts. I have a 98 with a 4.6L stroker, all coolant parts are new within the last year. High flow water pump, chrysler thermostat, chrysler ect sender, new hoses with the spring in the lower, new clutch fan and CSF new 3 row radiator. When cruising down the highway it is saying on my scanner pid that it is getting up to 235-240. I have pulled over when this is happening and with a non contact laser thermometer at the thermostat it is 210-215. At idle when scanner shows 217-222, with the thermometer is at 198-200. The gauge has shot up to the 250* range and instrument cluster warning light check gauges comes on like it is overheating. It is not overheating though, it has never boiled over or even pumped any coolant into the overflow. It has been the same amount in the coolant bottle. I have tested wiring to ground circuit and it was good, all other sensors on the ground circuits are working correctly with no problems. I ran a separate wire to the pcm pin for the signal of ECT to eliminate any problems with signal wire to pcm. I was pretty confident that the pcm was messing up, installed new programmed pcm with the same issue.
I am looking for any help or other avenues to look for a problem.
Thanks in advance

 

Interested too, as mine reads consistently low, like it shows 175-180 on the gauge, but actual temp is 210 or so.

For mine, I'm beginning to think I am getting an air bubble at the sensor, as I have removed the temp control valve in the heater circuit and just installed a shut off valve for summer.

 

Install an aftermarket cooling gauge

Install either an aftermarket or homebrew system that make physical contact with the vital areas (my IR gun has a probe with 10ft wire)

I am presuming that your first imperative is to make sure that your engine and cooling system is not experiencing high temps, as neither of the above is totally straightforward

 

I am planning on doing that to confirm the temp. I still need to figure the problem with the ect reading to the pcm. That could through off the air/fuel ratio