Code 24, Manifold Air Temperature (Mat) Sensor Circuit Low Temperature Indicated: Notes

The MAT sensor uses a thermistor to control the signal voltage at the ECM. The ECM applies 4-6 volts to the sensor. When air is cold, thermistor resistance is high, so ECM will see a high signal voltage. If air is warm, sensor resistance is low, so ECM will see a low voltage.

1. This verifies 4-5 volts is present at MAT sensor connector.
2. This checks ground side of MAT sensor circuit.
3. This determines if problem is caused by an open circuit or ECM.
4. This determines if Yellow/Black wire is open or ECM is defective.