Transmission Control Systems: Description and Operation

OVERDRIVE SWITCH
Vehicles equipped with an automatic transmission may have an overdrive switch. The operator disables or enables overdrive when the switch is depressed.

The overdrive system consists of a switch connected to the Powertrain Control Module (PCM) and an overdrive ON/OFF indicator lamp.

If overdrive is currently enabled, it is disabled when the operator depresses the overdrive switch. Conversely, if the operator already disabled overdrive, it is enabled when the switch is depressed. The overdrive lamp illuminates when overdrive is disabled.

Circuit T9 from the overdrive switch connects to the PCM. Circuit T9 provides the overdrive signal. Circuit Z1 provides ground for the switch.

In the START and RUN position, the ignition switch connects circuit A1 from fuse 12 in the Power Distribution Center (PDC) with circuit A21. Circuit A21 powers circuit F87 through fuse 21 in the fuse block. Circuit F87 supplies battery voltage for the overdrive lamp.

The PCM turns the overdrive ON/OFF indicator lamp ON or OFF by providing a ground for the lamp on circuit G68.

NOTE: The overdrive lamp is a Light Emitting Diode (LED).

OVERDRIVE SOLENOID AND TORQUE CONVERTER CLUTCH (TCC) SOLENOID
The overdrive solenoid and TCC solenoid are molded together. Circuit F86 supplies voltage to both solenoids. The PCM provides ground for the overdrive solenoid on circuit T60. The PCM provides ground for the TCC solenoid on circuit T6.