Since saturday, my temp gauge will not move at all and my cooling fan comes on as soon as i crank the car even on a cold morning. I've replaced the coolant temp sensor and the coolant temp sensor connector. Still having problems. My dad ran into the same problem in his new silverado and it was the thermostat stuck. One of my good friends is a mechanic and says the thermostat wouldn't cause either of these problems. Just want some input as to if the thermo is the cause of my headache or what else it may be.

 

3.8? or 3.4?

 

2001 3.8 5speed

 

It is definitely *not* the thermostat.

It is almost certainly the coolant temp sensor or the signal wire between the sensor and the PCM.

The Haynes manual I have has pretty crappy wiring diagrams but it shows the ECT have a dark blue wire going to the PCM and a black ground wire. Make sure that the sensor you replaced has those wire colors going to it.

There may be a separate sensor or switch for fan or gauge operation but probably not. By 2001 most of that stuff was driven by a single sensor.

 

I already replaced both of the parts you mentioned and it still has the same problems

 

you could always put a mechanical temp gadge in replace of it. sounds like a bad connection of some sort either from the computer or to your cluster.

 

An inop temp gauge combined with cooling fans coming on immediately following a cold start is a classic bad coolant temp sensor issue.

If it isn't the sensor you have to measure the resistance of the dark blue wire between the sensor and the PCM. Check the connector to verify that terminals aren't "sprung" (not making contact) or pushed back in the body. If that stuff checks out, the PCM is bad.

Just for kicks, disconnect the coolant temp sensor, turn the ignition switch to run, and measure the voltage you get between the two connector terminals. Wiring harness terminals that is... Don't maul the terminals or you'll *create* problems instead of fixing them.