GM Service Manual Online
For 1990-2009 cars only
Crank Request Signal: The scan tool displays Yes/No. The scan tool displays Yes when the powertrain control module (PCM) receives a crank request.

Ignition 1 Signal: The scan tool displays voltage. The scan tool displays the current voltage at the battery.

GEN L-Terminal Signal Command: The scan tool displays On/Off. The scan tool displays Off until the engine is started, then it will display On.

GEN F-Terminal Signal: The scan tool displays 0%-100%. The scan tool displays 0%-5% until the engine is running, then the percentage value varies depending on electrical loads.

TR Sw.: The scan tool displays Park, Reverse, Neutral, Drive 4, Drive 3, Drive 2 and Drive 1. The scan tool displays the position of the transmission range switch.