Park/Neutral Position Switch
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) determines when the vehicle is in Park or Neutral gear position through the Park/Neutral Position (PNP) switch. The Red/Black wire to the PCM is grounded by the PNP switch when the transmission manual selector is in either Park or Neutral gear position.