I have a 2003 Silverado with a 5.3L engine. I need to find the coolant temperature switch. NOT the coolant temperature sensor that is above the first cylinder, has two wires, and send info to the computer. I need to find the sender with one wire that sends info to the temperature gauge.

 

on most it is on the left front head above the 1st spark plug

 

Are you sure the temp gauge has a dedicated sensor? I haven't looked at the vehicle schematic since 2008, but I'm not sure why a separate sensor would be needed.

Note: these trucks have extremely common problems with the gauge cluster being inaccurate or completely out of control. If you're trying to diagnose an inaccurate temperature gauge, you may want to consider that the gauge itself is physically bad.

 

If you’re still needing an answer here...

There’s no direct circuit between the coolant temp sensor or switch and the instrument cluster. All coolant related information is data fed to the cluster from the PCM.

There’s a temp sensor above the #1 spark plug and a low coolant level switch in the reservoir/surge tank, both of which are wired to the PCM.