spurcap, what year is your truck? (helpful to put it in your sig)

The gauge on the dash is not accurate enough to determine anything other than "cold", "normal", and "you are screwed".

220k ohms suggests a temp higher than 85°C (190 F)

 

96 disco 1. Because I was giving operating temps I thought it was clear I was using a scan gauge.

I agree that it suggests a normal temp. Found a GM temp chart which was close to Rave that puts 222 ohm in the 190s if the sensors are similar. Perhaps I have a loose ground to the ECU causing the issue? Anyone know the easiest way to test ECU voltage? Where is it and does it come out easy? Maybe I knocked something while docking around with the cruise control...

 

I never got around to changing the temp sensor. I'm in North Alabama and my temp stays right at 186 (Ultragauge). My condenser fans do not work and with the a/c going is stays right about there as long as I am moving.
Ultragauge says I am in closed loop so I just let it keep doing what it is doing and not mess with it.
Don't know if this helps or not but maybe it might.

Going to be tracking down a drivetrain racket this weekend.

 

Thanks.

186 doesn't seem too off to me as the thermostat opens at 190F fully I believe so will be circulating below that. My 170s seems wrong. And after looking at sensor resistance (and trying 2 different sensors with same results) I am thinking it must be an electrical issue. Hopefully someone around here has some ideas of tracking down. My first guess is to check power and ground (i.e. voltage) to the ECU but not sure the best way to do that. I am useless with the electrical manual....

 

Fairly sure this is an issue not with the sensor or actual temp but with the ECU interpretation of the data
Today I checked all the ECU grounds and all looks good. Checking the power pins all seem fine except for pin 7 on the 18 pin connector c1033. This is called "power supply from main relay" and it was getting like 0.5v with both ignition on and off. Doesn't seem normal but wanted to confirm. And where can I look?

Also randomly today but unrelated my door sensor started thinking the door is open when it's shut and shut when its open. Electrical gremlins I think.

 

Ran a (reasonably) scientific experiment today. Bought a 2W 300 ohm resistor from electronics store, tested with ohm meter and got 301. Wedged ends of resistor into temp sensor connector. Started truck. Gauge reads 172 and change. Per RAVE should read 85C = 185F. Variance = under by 13F. Interestingly I had been monitoring my temps fairly constantly in the last few days and had been seeing in the 175F to 183F range. Adjusting this by 13F ==> 188-196F which is exactly the range I used to run. This seems fairly conclusive that it is something with the computer and my best guess is voltage.

To recap above, I have pulled the ECU and didn't get any bad grounds at the connectors, and the voltages were within 0.03V of what I got when going direct to the battery posts.

Two questions:
1) Any other ideas on where to track this down?
2) How much of a difference will this make to truck performance? Having a knowingly wrong # looking me in the face is bad enough but it is more important that this isn't substantially negatively impacting the truck's operation. I know at minimum it means it gets in closed loop later ...