The manifold air temperature sensor is located in the intake manifold. The MAT sensor reacts to the temperature of the air in the intake manifold and provides an input to the ECU to allow it to compensate for air density changes during high temperature operation.
See Figure 1
Disconnect the wire harness connector from the MAT and measure the resistance of the sensor with a high input impedance (digital) volt-ohmmeter. The resistance should be less than 1000 ohms with the engine warm. Refer to the resistance chart and replace the sensor if it is not within the range of resistance specified in the chart. Measure the resistance of the wire harness between ECU wire harness connector terminal D-3 and the sensor connector terminal, and terminal C-8 to the sensor connector terminal. Repair the wire harness if the resistance is greater than 1 ohm.