GM Service Manual Online
For 1990-2009 cars only
ATC Application: The scan tool displays a numeric valve. This value determines which model of transfer case is in the vehicle.

AWD Indicator: The scan tool displays ON or OFF. This parameter determines if the transfer case shift control module is commanding the AWD indicator on.

Encoder Channels P, B, A, and C: The scan tool displays ON or OFF. If a high voltage is displayed then the channel is OFF, if the encoder motor grounds the circuit and pulls the voltage low then the circuit is ON. The encoder channels allow the transfer case shift control module to determine what position the transfer case is in.

Enocoder Gear Position: A parameter on the scan tool that shows what mode the transfer case is currently in.

Encoder Supply Voltage: This parameter indicates the voltage that is being supplied to the encoder motor and can be 0-25 volts.

Mode Switch Return Voltage: The scan tool displays a range of 0-5 volts. This parameter indicates the voltage measured by the transfer case shift control module after the voltage has gone through the resistors in the mode switch. The transfer case shift control module reads this voltage to determine what mode the driver has selected.

Mode Switch Selected: This parameter indicates which mode is currently being selected.

Motor A Circuit Status: The scan tool displays ON or OFF. If ON is displayed this indicates battery voltage is being applied to the Motor A circuit.

Motor B Circuit Status: The scan tool displays ON or OFF. If ON is displayed this indicates battery voltage is being applied to the Motor B circuit.

Neutral Indicator: The scan tool displays ON or OFF. If ON is displayed this indicates the transfer case shift control module has requested the neutral indicator be turned on.

Software ID: The scan tool displays a numeric value which indicates which version of software is currently installed in the module.

AWD Indicator: The scan tool displays ON or OFF. If ON is displayed this indicates the transfer case shift control module has requested the AWD indicator be turned on.

TCS Indicator: The scan tool displays ON or OFF. If ON is displayed this indicates the transfer case shift control module has requested the TCS indicator be turned on.

4WD Low Indicator: The scan tool displays ON or OFF. If ON is displayed this indicates the transfer case shift control module has requested the 4WD low indicator be turned on.

4WD Low Active: The scan tool displays YES or NO. If YES is displayed this indicates the transfer case is currently in the 4WD low mode.

GM Part Number: The scan tool displays a numeric value. This parameter indicates the GM part number assigned to the module package (module, software, and calibrations).

Battery Voltage: The scan tool displays a range of 0-25 volts. This parameter indicates the voltage measured by the transfer case shift control module at its battery feed.

Ignition Cycles Since Last Current DTC: The scan tool displays a numeric value. This parameter indicates how many ignition cycles have occurred since last current DTC was set.

Service 4WD Lamp: The scan tool displays ON or OFF. This parameter indicates if the Service 4WD Lamp is being commanded by the transfer case shift control module.