Code 23, Mat Sensor Temp. Low - 3.8L & 4.3L CPI: Notes

ECM supplies and monitors a voltage signal (4-6 volts) to sensor. When temperatures are low, sensor resistance is high and ECM will see a high-monitored voltage signal. As temperature increases, sensor resistance decreases and voltage sensed by ECM drops.

1. This checks if Code 23 is a hard failure or an intermittent condition. Code 23 will set if engine is running for one minute, MAT sensor temperature is less than -22°F (-30°C) for 12 seconds and speed sensor signal is not present.
2. This simulates conditions for a Code 25. If scan tester displays a high temperature, ECM and wiring are not at fault.
3. This checks for continuity of sensor signal and ground circuits.