EGR Temperature Sensor: Description and Operation

The EGR gas temperature sensor is used to provide the ECM with information about EGR system operation. When the EGR valve is open, exhaust gas heats the sensor. When the valve is closed, the sensor cools. The ECM monitors this temperature change and memorizes the range across which the temperature varies under normal operation. If the ECM detects a temperature range smaller than that stored in memory (approx. 6°C / 11°F), it senses a fault. If the fault is noted on three consecutive measurements, a trouble code (32) will set. Testing is required to determine which component of the EGR system has failed. Measurements are taken when conditions exist such that the ECM "knows" the EGR valve should be either fully open or fully closed.

A separate trouble code (34) will set when the ECM recognizes malfunctions with the EGR sensor and/or its electrical connections and circuits. Note that this problem can occur even though the EGR system is functioning normally.

The ECM detects changes in sensor resistance that vary with temperature as follows:

Temperature °C(°F) Resistance K ohms

0 (32) 28
20 (68) 12.1
40 (109) 5.8
80 (176) 1.7