What is the Cylinder Head Temperature Sensor all about?

Your engine control module monitors and regulates nearly all of your engine’s performance based on temperature measurements. During cold conditions or cold starts, the engine requires more fuel to run well and maintain a higher idle speed. When the engine is warm, less fuel is required for the engine to run smoothly and efficiently. There are a couple of methods car makers have utilized to determine engine temperature, with the most common being a coolant temperature sensor.

The coolant temperature sensor regularly monitors the engine’s heat based on the temperature of the fluid circulating in the block and reports it to the engine control module. The ECM adjusts EGR flow, engine timing and many other things based on this information. For vehicles not equipped with a coolant temperature sensor, a cylinder head temperature sensor, or CHT sensor, is employed. It consists of two resistors encapsulated in one sensor to maintain a wide operating temperature of -40F to 260F. One resistor monitors the high temperatures and the other, the low temperatures, and reports them in a voltage reading to the ECM. From this reading, the engine control module infers the coolant temperature and bases its adjustments on it. If the CHT sensor isn’t reading correct voltages, you can experience issues ranging from long cranking times and low idle speeds on cold starts to stalling and hesitation on acceleration while the engine is warm.

Keep in mind:

• The cylinder head temperature sensor doesn’t measure the coolant temperature. Instead, it measures the metal temperature and infers the coolant temperature from that.
• Allow the engine to cool off before servicing the cylinder head temperature sensor.

How it's done:

• The cylinder head temperature sensor is verified that it needs to be replaced. The rubber head seal and connector are removed to access the sensor.
• The defective cylinder head temperature sensor is removed with a deep well socket to unscrew the sensor from the cylinder head.
• The new cylinder head temperature sensor is installed into the head and tightened to specifications.
• The electrical connection and rubber seal are reinstalled. The cylinder head temperature sensor is tested for operation with a scanner.
• The vehicle is road tested to ensure proper operation of the cylinder head temperature sensor.

Our recommendation:

The CHT sensor should last the life of your vehicle. It is an electrical component and can fail unexpectedly, and if it does, it will need to be replaced by one of our expert technicians. If you suspect you have a CHT sensor problem, have a trained technician diagnose the problem as monitoring the sensor is tricky and requires certain knowledge.

What common symptoms indicate you may need to replace the Cylinder Head Temperature Sensor?

• Long cranking time when trying to start your engine
• Difficulty with accelerating
• Engine stalling when at running temperature or when started cold
• Idle speed when the engine is cold stays very low

How important is this service?

The cylinder head temperature sensor can dramatically affect your engine’s performance if it is faulty. It may cause running issues while you are driving in traffic including stalling and hesitation. Have it diagnosed and repaired as soon as possible so you don’t put yourself in a potentially difficult or dangerous driving situation.