Exhaust Gas Temperature (EGT) Sensors: How Do They Work?

With emission legislation becoming more stringent lately, modern cars available today feature exhaust gas temperature (EGT) sensors. This move comes when engines are designed to be economical and environmentally friendly while continuing to deliver greater power. However, EGT sensors are especially prone to failure despite their popularity.

Because of this, you must know how they work to understand whether you can prevent unwanted breakdowns. Consequently, you can learn how to best repair this vital component and get back on the road. If you’re searching for this helpful information, look no further as this guide deeply looks at how EGT sensors work. Let’s get started.

What’s An EGT Sensor?

Before you approach an EGT sensor supplier to replace your malfunctioning EGT sensors, you must understand this component first. As the name goes, EGT sensors are crucial components for measuring the exhaust gas temperature. They’re also known as high-temperature sensors or exhaust temperature sensors.

Using the information collected by the EGT, sensors are later conveyed to the engine control unit, and you can use this information to know what action to take. Depending on the received data, the control unit can take different actions, including lowering the boost pressure and increasing the flow of coolant fluid. In addition, the EGT sensors also help increase oil flow and correct the mixture composition, and it does this by increasing fuel.

How Do EGT Sensors Work?

There are two kinds of EGT sensors, one with a negative temperature coefficient (NTC) sensing element and another comes with a positive temperature coefficient (PTC). The difference between these two is how they measure temperature.

The PTC element is the most common thermistor and works by increasing resistance as the temperature is continually on the rise. In contrast, the NTC sensing element features a low resistance at high temperatures and high resistance at low temperatures. For both the PTC and NTC thermistor, the temperature is assigned to the engine control unit’s (ECU) resistance, and the proper action is taken.

The installation position of the EGT sensors differs depending on the purpose they’re looking to achieve. Some of the possible installation positions include:

  • Downstream or upstream of the catalytic converter
  • Upstream or downstream of the diesel particulate filter (DPF)
  • The components of the NOx reduction system
  • Upstream or downstream of the turbocharger

The role of EGT sensors differs in diesel and petrol engines. In diesel engines, the EGT sensors come in handy when monitoring the temperatures of the DPF to determine the ideal temperature for regeneration. This information helps establish the correct regeneration temperature that helps lower exhaust emissions. In most cases, three or more EGT sensors are installed into the exhaust, one after the particulate filter, the other before the DPF, and the last one fixed to the exhaust.

In contrast, EGT sensors in petrol engines are tasked with safeguarding essential car components from higher temperatures. They’re a common addition to downsized petrol engines that are more susceptible to excessive temperature increases. The two main components that EGT sensors monitor are the catalytic converter and turbocharger.

When the EGT sensors detect a drastic rise in temperatures in these two components, it relays this information to the ECU. The ECU will consequently increase the volume of fuel entering the catalytic converter or increase the fuel quantity added for the catalytic converter and fuel consumption. As a result, this will reduce the turbocharger’s boost pressure by cooling the catalytic converter.

Why Do EGT Sensors Fail?

Despite playing such an integral role, EGT sensors fail at times due to unreasonably high temperatures, which can exceed 900℃ sometimes. Another thing that can destroy EGT sensors is twists or bends that eventually cause the breaking of wires. This causes them to be especially susceptible to damage when replacing other components found in the exhaust system.

Besides, the loosening of internal components due to extreme vibrations, also known for destroying wired sensors, can also destroy EGT sensors. The damage to these sensors can also arise due to contact with other fluids such as antifreeze or oil, resulting in inaccurate readings or a fall in tolerance.

If you suspect that the EGT sensors are about to fail, some symptoms can best indicate a malfunction, and these include:

  • A fall in your car’s fuel efficiency happening because the EGT sensors are conveying incorrect voltages, thereby causing the DPF regeneration process to take longer. Hence, this leads to an increase in fuel use.
  • Premature component failure of crucial parts such as the internal engine elements or the exhaust system because of excessively high temperatures
  • Engine light blinking when the ECU notices an error in the signal or sensor.
  • Failed emission test that happens due to malfunction of the EGT system without the check engine light being triggered
  • Needless DPF regeneration due to faulty sensors that can inconvenience the vehicle owner

There are different ways you can troubleshoot the issues, such as:

  • Check the sensor to look for the accumulation of contaminants and consequently use a clean and dry cloth.
  • Inspect the wiring to look for the slightest damage or breaks that might fall short to the ground.
  • Carry out an electric test and use a diagnostic tool to read for the slightest fault codes.
  • Use a separate infrared measurement gadget to test the EGT sensor and compare these readings to the live data you get with the diagnostic tool. Run your car’s engine to increase the exhaust temperatures and compare these readings.
  • Check the connectors for possible signs of loose connections or corrosion.

By doing any of this, you’ll be able to diagnose a defective EGT sensor.


Today’s modern petrol and diesel cars incorporate EGT sensors across different sections in the exhaust gas system to make them function better. However, if you aren’t that tech-savvy to understand the mechanical details of your car, knowing how the EGT sensors work can be a bit overwhelming. Fortunately, this guide has outlined everything you need to know, and understanding this will come in handy when you need some repair done.