What is an NTC EGT Sensor?

1. Working Principle

The NTC EGT Sensor uses NTC (Negative Temperature Coefficient) thermistor technology, where the resistance drops rapidly as the temperature rises.

When the temperature of the three-way catalytic converter rises abnormally, the sudden drop in resistance triggers the exhaust temperature warning light on the vehicle's dashboard, alerting the driver to take timely action.

2. Response Speed

NTC thermistors are extremely sensitive to temperature changes; even a tiny temperature rise will elicit a feedback signal within milliseconds.

This high-speed response ensures that the protection mechanism can be activated immediately in the event of engine misfire, incomplete combustion, or other abnormal operating conditions.

3. Application Scope

Suitable for exhaust temperature monitoring in various mainstream passenger and commercial vehicle brands.

By monitoring exhaust temperature in real time, it prevents the catalytic converter from failing due to overheating, protecting the reliability of the engine and emission system.

4. Technical Advantages

High sensitivity, high temperature resistance, and compact structure, facilitating installation in complex engine compartment environments.

Seamless integration with the vehicle's electronic control unit (ECU) enables accurate fault diagnosis and protection functions.

How to perform on-site diagnostics on an NTCEGT sensor using a multimeter or dedicated tester?

1. Preparation

Ensure the vehicle is off and the key is removed to prevent accidental circuit activation.

Locate the sensor's wiring terminals, typically two wires (signal and power/ground), and record their locations.

2. Measuring Resistance with a Multimeter

Set the multimeter to the resistance (Ω) range and connect the multimeter probe to the two wires of the sensor.

Read the resistance value at room temperature (approximately 20°C), referring to the manufacturer's reference resistance range (e.g., 1kΩ ± 10%).

If the resistance deviates significantly from the reference range, the sensor may have an internal short circuit or open circuit fault.

3. Verifying Temperature Characteristics using Heating

Use a hot air gun or heating plate to controllably heat the sensor (gradually increasing the temperature to 150°C).

Simultaneously monitor the resistance change on the multimeter; the resistance should decrease exponentially with increasing temperature.

Plot a resistance-temperature curve. If the curve deviates from the standard NTC curve, the sensor's temperature response characteristics are compromised.

4. Diagnostic Procedures for Dedicated Testers

Insert the probe of the dedicated EGT sensor tester into the sensor connector. The instrument will automatically apply an analog current and read the real-time resistance.

The instrument displays the current resistance value and corresponding temperature. If the temperature display is abnormal or the instrument alarms, the sensor is diagnosed as faulty.

Some advanced testers also have a "self-test" function, detecting wiring harness continuity, short circuits, open circuits, and signal noise levels, providing a more comprehensive diagnostic report.