Circuit/System Description
WARNING: This page is about a different car, the 2007 Suzuki XL7. However, it is still accessible from the selected car via links, so may be relevant.
The transmission range (TR) switch is an integral part of the transmission control module (TCM). As the gear range selector lever is moved, the state of the Starter Inhibit Circuit may change, causing the circuit to open or close. An open circuit indicates a drive range and a low voltage signal, 0 volts, at the engine control module (ECM). A closed circuit indicates PARK or NEUTRAL and a high voltage, 12 volts, signal at the ECM.
The ECM uses the Starter Inhibit circuit status from the TCM in order to enable starter operation.