What Is An Exhaust Gas Temperature (EGT) Sensor?

What Is An Exhaust Gas Temperature (EGT) Sensor?

Exhaust gas temperature sensors (EGT) are becoming more common in modern-day vehicles due to increasingly strict emissions regulations. However, they have a high failure rate, making repairs for them more in demand.

If you’re unfamiliar with EGTs, this article will explain what they are, why they fail, and how to fix them. Keep reading.

Definition: Exhaust Gas Temperature Sensor 

The exhaust gas temperature sensor, as its name implies, gauges the temperature of the exhaust gas. The engine control unit (ECU) receives this information and takes the necessary actions. 

For instance, the ECU might increase the fuel injected into the catalytic converter or decrease the boost pressure for the turbocharger if the sensor detects temperatures that are too high.

Typically, this sensor protects more parts or the critical components of the vehicle from higher temperatures brought on by downsized engines in petrol engines.

Diesel particulate filters (DPFs) are also monitored using exhaust gas temperature sensors to reduce harmful emissions and ensure that the regeneration temperature is correct.

The exhaust can have three or more sensors, which are located before the turbo, before the DPF, and after the particulate filter.

Types Of EGT Sensors

EGT sensors come in two types: a positive temperature coefficient (PTC) and a negative temperature coefficient (NTC). 

“Positive Temperature Coefficient” means the resistance rises as the temperature increases. Resistances of PTC temperature sensors vary linearly, and their detection range extends from -70°C to 900°C. PTC’s EGT sensor incorporates PT200 sensing elements manufactured by thin film technology. It can precisely detect temperature variations and has a 200Ω (Ohm) characteristic at 0°C.

The “Negative Temperature Coefficient,” or NTC, describes the resistance decreasing as temperature rises. NTC temperature sensors detect temperatures ranging from -40°C to 900°C, depending on the thermistor type. A logarithmic scale is used to describe resistance variation. 

In addition to the press-formed construction with embedded conductors, NTC EGT sensors are designed to meet specific temperature sensitivity ranges. A temperature change can have a significant impact on it.

Causes Of Exhaust Gas Temperature Sensors Failure

The primary cause of EGT sensors failing is when temperatures rise to a greater degree, reaching over 900°C in extreme cases. High vibration may also weaken internal connections, as with all wired sensors.

Sometimes, proper maintenance and checking can prevent EGT sensors from failing. Because any twisting or bending can break the wire, they are particularly vulnerable to harm while other exhaust system components are being replaced. Combined with contamination from fluids like antifreeze or oil, a sensor’s response characteristics may suffer a setback, causing it to generate incorrect readings and drift outside of tolerance.

Symptoms Of Faulty EGT Sensor

When a vehicle’s EGT sensor is faulty, it can negatively affect its after-treatment system, resulting in the following symptoms:

  • Check engine light: The check engine light will turn on if the ECU notices an issue with the signal or sensor.
  • Fuel efficiency is reduced: The DPF regeneration process may take longer if the sensor transmits erroneous voltages, increasing fuel consumption.
  • Unnecessary regeneration of the DPF: Defective sensors can also result in unneeded regenerations, which is inconvenient for the vehicle owner.
  • Failure of a component: Elevated exhaust temperatures may cause other exhaust or internal engine components to fail prematurely.
  • Failed emissions test: A false reading can result in an EGR system malfunction without setting off the check engine light. An emissions test may fail as a result of this.

Troubleshooting An EGT Sensor

Consider these steps when troubleshooting the EGT sensor:

  • Utilize a diagnostic tool to do electronic tests and read trouble codes.
  • Look for rust or lose connections in the connectors.
  • To prevent a short to the ground, inspect the wiring for any cracks or other damage.
  • Check the sensor for any accumulation of pollutants and clean it as necessary with a dry, clean cloth.
  • Use a different IR measurement equipment and compare the results to the live data acquired using a diagnostic tool to test the sensor. Compare the data after running the engine till the exhaust reaches a higher temperature.
  • If the vehicle ignition is on, disconnect the EGT sensor’s plug and measure its voltage at its connector – it should be five volts. Otherwise, verify that the ECU is receiving power from the wire.


To conclude, a sensor in the automobile exhaust system measures the exhaust gas temperature. When a vehicle does not receive routine maintenance, its power can decrease while driving, causing irreparable damage to its components. 

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