[BNaylor]

Is this a LTZ or Police Special 9C3? What problem are you having?

The engine coolant temp sensor (ECT) on a L36 engine is located below the thermostat and housing. Just follow the upper radiator hose to the thermostat housing. You'll see the electrical connector. You can ohm it out with a digital mulitmeter to check for calibration.

Both cooling fans should turn on when the A/C is on, otherwise the coolant temperature has to reach around 220 degrees before the fans will tun on with A/C off and referencing to just the ECT.

See below for cooling fan operation.

Fans OFF: The coolant temperature is less than about 220°F (104°C) or A/C refrigerant pressure is less than 190 psi (A/C off).

Low-Speed:The coolant temperature is between about 220°F (104°C) and 230°F (110°C) or A/C refrigerant pressure is more than 190 psi (1310 kPa).

High-Speed:The coolant temperature is above about 230°F (110°C) or A/C refrigerant pressure is more than 240 psi (1655 kPa) or when certain DTCs are set.