Transmission Range Switch
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
The Transmission Range (TR) switch is part of the Park/Neutral position and back-up light switch assembly and is mounted on the transmission manual shaft. The TR switch is a multi-signal switch. The Powertrain Control Module (PCM) supplies ignition voltage to the TR switch on four signal circuits, "A", "B", "C", and "D". Each gear selector lever position grounds one or more of the signal circuits in a unique pattern. To determine the gear range selected by the driver, the PCM compares the voltage combination on the signal circuits to a TR switch combination table stored in memory.