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 on the battery positive voltage circuit of the module or the 72-08 battery voltage message from the body control module (BCM) over class 2 lines.

GEN L-Terminal Signal Command: The scan tool displays On/Off. The scan tool displays Off until the engine is running, then the powertrain control module (PCM) supplies then 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 PCM.

IMS: The scan tool displays Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, INVALID, and OPEN. The scan tool displays the physical position of the internal mode switch (IMS) of the transmission.

Starter Enable Relay Circuit Status: The scan tool displays Fault/OK/Invalid State. The scan tool displays Fault until the ignition is placed into the Crank position then OK is displayed.

Starter Relay Command: The scan tool displays ON/OFF. The scan tool displays Off until the ignition is placed into the CRANK position, then it reads On.

Starter Switch: The scan tool displays ON/OFF. The scan tool displays ON when the ignitions switch is in the Start position.