Code 23: Mat Sensor Temp Low: Notes
WARNING: This page is about a different car, the 1990 Chevrolet Corsica, 1990 Chevrolet Cavalier, and 1990 Chevrolet Beretta. However, it is still accessible from the selected car via links, so may be relevant.
The ECM supplies and monitors a voltage signal (4-6 volts) to the sensor. When temperatures are low, sensor resistance is high and the ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by the ECM drops.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- This checks if Code 23 is because of a hard failure or an intermittent condition. Code 23 will set if engine has been running for a precalibrated period of time and signal voltage indicates a MAT temperature less than -22°F (-30°C).
- This simulates conditions for a Code 25. If the "Scan" tester displays a high temperature, the ECM and wiring are not at fault.
- This checks for continuity of sensor signal and ground circuits. If ground circuit is open there may also be a Code 33 or Code 21 stored.