Circuit Operation

The PCM (terminal 124) applies 5 volts to the A/T fluid temperature sensor output terminal (terminal 1).
The A/T fluid temperature sensor circuit is grounded to the PCM (terminal 57).
When the A/T fluid temperature is cold, the A/T fluid temperature sensor resistance is high. When the A/T fluid temperature is hot, the A/T fluid temperature sensor resistance is low.

Fig 1: A/T Fluid Temperature Sensor System Circuit Diagram & Connector Identification

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.