how do i change the coolant temperature sensor on a 2003 Trailblazer. I have already purchased the part but i seem not to find where the sensor is located.

Which engine?

Sorry, the engene is a 4.2, 2 wheel drive.

The sensor is locatedon the driver's side near the front of the engine. It screws into the block behind the alternator. To replace it, you will need to remove the serpentine belt and the alternator and drain the cooling system down to below the level of the sensor. Looks like the electrical connector plugs to the sensor from above -- you will pull the connector straight up to remove it. The connector has two wires, one yellow and the other black. Hopefully, this will help you to locate it.

Good luck

That really helped, thank you so much.