Where is the temperature sending unit on a 2006 lacrosse cxl

Coolant sender unites do fail from time to time but before taking it out make sure you have enough coolant in the system for the sender to work . Often people will think there car has fixed itself when its running hot and then the temperature gauge goes down to nothing . this just means theres no fluid in the system at the sender . without the fluid there the sender cannot send a temp so it goes to zero. So before replacing the sender make sure your fluid level is up to proper levels. Hope this helps

"abbyshepard10 the cause could be a bad Engine Coolant Temperature (ECT) sensor.

3.6 L engine

3.8L engine"