Other than the TR (Transmission Range) Sensor (aka MLPS - Manual Lever Position Switch), there are no switches on or in the CD4E.
The O/D cancel switch is mounted on the shift lever. It is not required for normal operation. It is a momentary contact switch that, when pressed, tells the PCM that the drivers wishes to lock out overdrive. The PCM then implements a contol strategy that disengages O/D or keeps it from engaging, depending on current driving conditions.
Steve
