Engine Coolant Temperature Sending Unit - Repair or ReplaceIf your Engine Coolant Temperature sender has failed, you may notice one of several symptoms: your Temperature gauge doesn?t move, your Engine overheats without warning, your radiator fans don?t Switch on, or they don?t Switch off. If your Toyota has any of these symptoms, it's a good idea to let a trained Toyota technician perform an inspection. Calif. Type A. To 03/1997. From 12/2002. Vendor:denso. Japan Built Part.