What is the Coolant Temperature Switch (Sensor) all about?

The coolant temperature switch, also called the coolant temperature sensor, is a switch that reads the engine coolant temperature and sends a signal to the engine control module, or ECM, to control other functions of engine operation such as the air-fuel ratio.

It is also called a switch because on some cars, it is used to turn on the engine cooling fan at a specific temperature. This aids in the engine warm-up process as well as keeping the engine at a safe operating temperature.

Keep in mind:

• The coolant temperature switch is a crucial part of the cooling system. If faulty, it can cause severe internal engine damage due to overheating, incorrect air-fuel ratio, or incorrect ignition timing. It can also cause shorter life to the cooling fan motor or other electrical components of the cooling system.
• Some vehicles are equipped with a separate sensor to display the engine temperature to the driver via the temperature gauge.

How it's done:

• The Coolant Temperature Switch is verified that it needs to be replaced. The coolant is drained until the switch is exposed.
• The defective Coolant Temperature Switch is removed by disconnecting the connector and removing it from the manifold.
• The new Coolant Temperature Switch is installed into the mounting hole in the manifold and the electrical connector is reconnected. The coolant is then refilled.
• The Coolant Temperature Switch is tested for operation, codes cleared, and retested to ensure all codes have been resolved.
• The vehicle is road tested to ensure proper operation of the Cooling System.

Our recommendation:

If you suspect that your coolant temperature switch has failed, have one of our licensed mechanics come out immediately to diagnose the problem.

What common symptoms indicate you may need to replace the Coolant Temperature Switch (Sensor)?

• Check Engine light on
• Engine overheating
• Cooling fan runs intermittently
• Engine misfires, stalls, or idles roughly
• Erratic coolant temperature

How important is this service?

This part, when faulty, could cause the fan to run intermittently or not at all, which in turns causes overheating or overuse of the cooling fan motor. Whenever overheating occurs, severe engine damage is a possibility.

The engine air-fuel ratio is what keeps it running smoothly. If the ratio gets skewed, the engine will have poor fuel economy and run poorly or not at all. The coolant temperature switch is important because it gives the ECM the information it needs to make this calculation and run the engine optimally. YourMechanic will be able to tell you if this part is performing correctly.