So ive noticed that when i go to start my truck even if its been sitting all night and not running for almost 10 hours, as soon as i start it up my temperature needle shoots right up to the middle of the guage. Ummmm, could this be bad? its never over heated on me before and it doesnt seem to be having any problems, what could be wrong?

 

Coolant temperature sensor could be bad.

Your engine has two, one for the PCM, one for the gage.

Gage sensor should read 16.0 ohms hot and 275 ohms cold. Obviously , those values will vary, showing whatever the ambient/actual temperature of the sender is at that moment. If you are going to test it, just immerse in pans of cool / hot water while the meter is connected.

Or, replace the sensor. The one you are looking for has the red wire with a white stripe (RD/WH).

 

In your case, and easy way to see if it is the sensor that's causing the gauge to read half scale, when cold, is just unplug the sensor and see if the gauge goes to cold. If it stays at half-scale, with the sensor unplugged, then the problem is with the gauge, NOT the sensor.

 

well now its acting normal, this morning it was all the way down when i started it up this morning (like it should be) and it just increased as i drove like normal....maybe it was just an electrical freak out? lol idk

 

Could be a faulty connection, or corrosion on the wires causing it to read erratically. I would unplug it, clean everything, then hook it back up and hope for the best.

 

Since the resistance of the sensor drops with increased temp, any additional resistance with a "faulty" connection would make the gauge read too low, not too high, as his case.