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Home >> Geo >> 1990 >> Storm Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Code 23B, Manifold Air Temperature (Mat) Sensor Circuit High Temperature Indicated >> Notes
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Code 23B, Manifold Air Temperature (Mat) Sensor Circuit High Temperature Indicated: Notes

The MAT sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies 4-6 volts on Purple/Black wire to sensor. When manifold air is cold, the sensor (thermistor) resistance is high and the ECM sees a high voltage. As the air warms, the sensor resistance becomes less and the voltage drops.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This checks if Code 23B result from a hard failure or an intermittent condition. Code 23B sets if MAT temperature greater than 293°F (145°C) is detected for a time longer than 2 seconds.
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