Code 23: Mat Sensor Signal Volt High
The MAT sensor is used in conjunction with the MAF sensor so the ECM can accurately compensate airflow readings based on temperature. Code 23 will set if a signal voltage indicates a manifold air temperature less than -40°F (-40°C) for 4 seconds. Due to conditions necessary to set a Code 23, SERVICE ENGINE SOON light will stay on only while the fault is present.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- The "Scan" tester may not be used to diagnose this fault, due to the ECM transmitting default values. A Code 23 will set, due to an open sensor, wire or connection. This test determines if the wiring and ECM are okay.
- If the resistance is greater than 25,000 ohms, inspect air cleaner for presence of ice. If okay, replace the sensor. INTERMITTENTS is located in H - TESTING W/O CODES article.
NOTE:
A "SCAN" tool may not be used to diagnosis this fault, Due to the ECM transmitting "DEFAULT" (Substitute) values when the fault is present.