GM Service Manual Online
For 1990-2009 cars only
Battery Voltage: The scan tool displays 0-20 Volts. The scan tool displays the voltage as received by the body control module (BCM).

Crank Request Signal: The scan tool displays Yes/No. The scan tool displays No until the ignition is placed into the START position then Yes is displayed.

GEN F-Terminal Signal: The scan tool displays 0-100%. The scan tool displays 0-10% until the engine is started and the engine control module (ECM) receives a signal from the generator then OK is displayed.

GEN L-Terminal Signal Command: The scan tool displays On/Off. The scan tool displays Off until the engine is running, then the ECM supplies the percentage value varies depending on electrical loads

Ignition 1 Signal: The scan tool displays 0-20 Volts. The scan tool displays the voltage as received on the Ignition 1 circuit to the ECM.

PNP Switch: The scan tool displays Park, Neutral and In Gear. The scan tool displays the physical position of the PNP switch.

Starter Relay Command: The scan tool displays ON/OFF. The scan tool displays OFF until engine start has been requested, then it reads On.

Starter Relay Circuit Status: The scan tool displays Incomplete, Short Gnd, Open, Short to B+ and OK. The scan tool displays status of the starter relay control circuit.

TR. Sw.: The scan tool displays Park, Reverse, Neutral, Drive 5, Drive 4, Drive 3, Drive 2, and Drive 1. The scan tool displays the physical position of the transmission range switch.