GM Service Manual Online
For 1990-2009 cars only
Battery Voltage Signal: The scan tool displays 0-20 Volts. The scan tool displays the voltage as received by the module or the 72-08 battery voltage message from the body control module (BCM) over class 2 lines.

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.

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 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 Control Circuit : The scan tool displays Fault/OK/Invalid State. The scan tool displays Fault until the starter relay control circuit is grounded then OK is displayed.