Overdrive/Override Switch

PURPOSE
On vehicles equipped with an automatic transmission and overdrive, the powertrain control module (PCM) regulates the 3-4 overdrive up-shift and downshift through the overdrive solenoid.

OPERATION
This solenoid is located in the transmission. An overdrive/override push-button switch is located at the end of transmission shift lever. This solenoid is located in the transmission.

An overdrive/override push-button switch is located at the end of the transmission shift lever.

The overdrive/override push-button switch is normally open (overdrive allowed) when the lamp is not illuminated. It momentarily closes (overdrive not allowed) when the operator presses the switch and the lamp is illuminated. Overdrive will revert to ON (lamp off) each time the ignition switch in turned on. The transmission downshifts if the operator presses the override switch while in overdrive.

CIRCUIT OPERATION
Automatic transmission equipped vehicles may have an overdrive switch. The operator disables or enables overdrive when the switch is depressed.

The overdrive switch consists of a switch connected to the Powertrain Control Module (PCM), an illumination lamp 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 over-drive, it is enabled when the switch is depressed.

Circuit T6 from the overdrive switch connects to cavity C13 of the PCM and provides the overdrive signal.

The PCM turns the overdrive ON/OFF indicator lamp ON or OFF by providing a ground for the lamp on circuit T18.