GM Service Manual Online
For 1990-2009 cars only
Battery Voltage: This parameter indicates battery positive voltage inputted from the main relay to the PCM.

PNP Switch: The scan tool displays Park/Neutral when the transmission is in Park or Neutral, and In Gear when the transmission is operating in forward or reverse gears.

Starter Switch: This parameter displays Cranking when the PCM is receiving a signal indicating that the engine starter motor is cranking. The scan tool displays Released when the ignition is on.