DTC 23

The MAT Sensor uses a thermistor to control the signal voltage to the ECM.

The ECM applies a voltage (4-6 volts) on CKT 9 to the sensor. When the air is cold the sensor (thermistor) resistance is high, therefore the ECM will see a high signal voltage. If the air is warm, the sensor resistance is low therefore the PCM will see a low voltage.

Code 23 will set if:

^ A signal voltage indicates a manifold air temperature below 38°C (-36.4°F).
^ Time since engine start is 1 minute or longer.

Due to the conditions necessary to set a Code 23, the "Check Engine" light will only stay "ON" when both of the above conditions have been met.

1. A Code 23 will set due to an open sensor, wire, or connection. This test will determine if the wiring and ECM are OK.
2. If the resistance is greater than 25,000 ohms replace the sensor.