Circuit Description
WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) uses signals from the Vehicle Speed Sensor (VSS) and the Crankshaft Position (CKP) sensor to detect the actual gear position. The PCM then compares the actual gear with the shift schedule in the PCM memory to detect mechanical trouble of the shift solenoid #2.