Coolant Temperature Sensor

Coolant temperature sensor is located in upper radiator hose inlet housing. Sensor is a thermistor type, which provides ECU with engine temperature information. ECU uses this information to control air/fuel mixture, ignition timing, idle speed, exhaust gas recirculation system and canister purge system. On Q45, this input is also used in calculating ECU control of variable valve timing.

To determine engine temperature, ECU supplies and monitors a voltage signal to coolant sensor. As engine temperature increases, sensor internal resistance decreases, causing ECU monitored voltage to decrease as more signal voltage passes through sensor to ground.