The coolant temperature switch (CTS) provides you with alerts when the engine temperature is rising or when it is overheating. It is also called the coolant temperature sensor, and it is an important part of keeping you safe and your vehicle running well.
Coolant from inside the cylinder heads and engine block absorbs heat from the cylinders while your vehicle is running. The CTS detects these changes in temperatures and alerts the powertrain control module (PCM). The message the sensor sends to the PCM affects the overall operation of the engine because much of the fuel, emissions, ignition, and drivetrain functions are handled by the PCM. Therefore, these functions are affected by the operating temperature of the engine.
If the PCM gets a cold reading from the CTS, the injector pulse width is increased to create a richer fuel mixture. This prevents hesitation while the engine is warming up. Once the engine is warm, the PCM reduces the mixture to make it leaner. The PCM cycles the cooling fan on and off to make sure the engine stays cool and to prevent it from overheating. The PCM cycles this by using information from the coolant temperature sensor.
The coolant temperature switch can go bad over time, whether it is due to wear and tear, or an electrical issue. At some point, your coolant temperature switch may need to be replaced by a professional mechanic.
Since the CTS can go bad, you should be aware of the symptoms it gives off before it completely fails.
Signs your coolant temperature switch needs to be replaced include:
- Poor fuel economy
- Black smoke coming from the exhaust pipe
- Trouble starting your vehicle even after reaching normal operating temperature
- Your vehicle fails an emissions test
- You vehicle is constantly overheating
- The temperature sensor is not consistent and behaves erratically
- Check Engine Light comes on
- Engine stalls or has a rough idle
The CTS is an important part of your vehicle, because without it, your engine will run poorly and overheat on a regular basis. Eventually, if left as is, the engine will go bad and the vehicle will become inoperable.