Overdrive/Override Switch

DESCRIPTION
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. This solenoid is located in the transmission. The PCM circuit for overdrive is controlled by inputs from the engine coolant temperature sensor and vehicle speed sensor.

LOCATION
An overdrive/override push-button switch is located on the instrument panel.

OPERATION
If coolant temperature and vehicle speed are not within the preset PCM specifications, the PCM will not allow the transmission to shift into overdrive. These preset PCM specifications must be met before the push-button switch will be allowed to control overdrive operation.

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