No, not the temp gauge, it is hooked to a 1 wire sender that is just used for the drivers info, find the 1 wire sender, remove the connector, turn key on, ground that 1 wire, gauge needle should go to full Hot, if that happens then replace the sender, if it doesn't happen then there is a wiring or gauge issue.
There is a 2 wire Sensor that looks similar to the sender, it is used only by the computer.
It is called the ECT(engine coolant temp) sensor.
Yes, computer does use this sensor to set a Rich fuel mix when engine is cold, like the choke plate did on a carb engine.
When you cold start the engine the idle should be about 1,100rpms, then as engine warms up the idle should start to drop with coolant temp going up.
When engine is fully warmed up, above 1/3 and below 1/2 on gauge, the "target idle" should be set, 700 for manual, 800 for automatic.
If the above happens the ECT sensor is working.
If ECT is not working you could have cold start and running issues when cold, or poor MPG if computer thinks engine is cold all the time, it wouldn't cause your current described symptoms, and computer monitors ECT sensor so it would turn on the Check Engine Light(CEL) if sensor wasn't changing when engine was running.
Last edited by RonD; 03-30-2015 at 11:23 AM.