Code 23B - Manifold Air Temperature (Mat) Sensor Circuit (High Temperature Indicated): Notes

The MAT sensor uses a thermistor to control signal voltage to the ECM. The ECM applies 4-6 volts on circuit No. 472 to MAT sensor. When manifold air is cold, sensor resistance is high and ECM will see a high voltage. As air temperature increases, sensor resistance decreases and the voltage drops.

1. This determines if Code 23B is the result of a hard failure or an intermittent condition. Code 23B will set if MAT temperature is indicated to be greater than 275°F (135°C) for more than 255 seconds.