B15 Transmission Internal Mode Switch

WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.

Circuit/System Description - B15 Transmission Internal Mode Switch

The transmission internal mode switch is a sliding contact switch with 5 switches. The TCM provides a signal circuit to 4 of the contacts represented as Signal A, Signal B, Signal C, and Signal P. The TCM also provides a low reference signal. The four signal inputs to the TCM indicate the position of the transmission manual shaft. The input signal at the TCM is High when the switch contact is open, and Low when the switch contact is closed to the low reference.

One contact switch is used by the ECM to determine if the transmission is in park or neutral for engine start enable. The ECM provides a signal circuit to the neutral start switch. The Q8 Control Solenoid Valve Assembly provides a pass through connection. The park/neutral switch is closed when the transmission is in neutral or park, and open when the transmission is in reverse or a forward range