GM Service Manual Online
For 1990-2009 cars only

The automatic transfer case (ATC) Scan Tool Data Definitions contain a brief description of all ATC related parameters available on the scan tool. The scan tool data list is arranged in alphanumeric order.

ATC Aplication: Displays alphanumeric characters which show the transfer case model.

ATC Slip Speed: Displays a range of 0-8192 RPM. This parameter indicates the RPM difference between the front and rear propshafts.

AWD Enabled: The scan tool displays YES or NO. This parameter indicates if the transfer case shift control module is currently attempting to prevent front to rear propshaft slip.

Front Propshaft Signal Fault: The scan tool displays YES or NO. YES indicates a DTC C0305 (Front Speed Sensor Malfunction) has been detected, but the code will not set unless the fault is present for 30 seconds.

Front Propshaft Speed: Displays a range of 0-8192 RPM. This parameter indicates the rotational speed of the front propshaft.

Ignition 3: Displays a range of 0-25.5 volts. This parameter indicates the voltage measured by the transfer case shift control module at its ignition feed.

Last Adapt Highest PWM: Displays a range of 0-100 percent. This parameter indicates the highest duty cycle applied to the ATC motor during the last slip event.

Motor Ground Circuit Open: The scan tool displays YES or NO. When the ATC encoder/motor relay is commanded ON and the ATC transistor is commanded ON, both of which are integral to the transfer case shift control module. YES indicates no current flow and system voltage is sensed at both Motor A and B terminals.

Motor A or B Circuit Fault: The scan tool displays YES or NO. YES indicates that one of the above motor circuit faults has been detected.

Motor A or B Circuit Open: The scan tool displays YES or NO. When the ATC motor relay is commanded ON but the ATC transistor is commanded OFF, YES indicates no current flow and no voltage is sensed at the Motor B terminal.

Motor A or B Short to Gnd.: The scan tool displays YES or NO. When the ATC motor relay is commanded ON but the ATC transistor is commanded OFF, YES indicates that current is flowing through part of the circuit to a short to ground and that no voltage is sensed at the Motor B terminal.

Motor A or B Short to Volts: The scan tool displays YES or NO. When the ATC motor relay is commanded off, YES indicates that voltage is sensed on either the Motor A or B terminals.

Rear Propshaft Signal Fault: The scan tool displays YES or NO. YES indicates a DTC C0300 (Rear Speed Sensor Malfunction) has been detected, but the code will not set unless the fault is present for 30 seconds.

Rear Propshaft Speed: Displays a range of 0-8192 RPM. This parameter indicates the rotational speed of the rear propshaft.

Slip Adapt PWM: Displays a range of 0-100 percent. This parameter indicates the duty cycle applied to the ATC motor.

Software ID: The scan tool displays a four-digit number. This parameter indicates the transfer case shift control module calibration version number.

TP (Throttle Position) Angle: Displays a range of 0-100 percent. The TP Angle is computed by the VCM from the TP sensor voltage. The TP angle should read 0 percent at idle and 100 percent at wide-open throttle (WOT).