The Automatic Transfer Case (ATC) Scan Tool Data Definitions contain a brief description of all ATC related parameters available on the scan tool. The list is in the order it appears on the scan tool.

2WD High Indicator Light: The scan tool displays On or Off. This parameter indicates On when the transfer case shift control module commands the 2WD high indicator light On.

4WD High Indicator Light: The scan tool displays On or Off. This parameter indicates On when the transfer case shift control module commands the 4WD high indicator light On.

4WD Low Indicator Light: The scan tool displays On or Off. This parameter indicates On when the transfer case shift control module commands the 4WD low indicator light On.

ATC Slip Speed: The scan tool displays a range of 0-8,192 RPM. This parameter indicates the RPM difference between the front and rear propshafts.

Auto 4WD Indicator Light: The scan tool displays On or Off. This parameter indicates On when the transfer case shift control module commands the auto 4WD indicator light On.

Commanded Mode Indicator: The scan tool displays a range of Auto 4WD to 4WD Low. This parameter indicates which mode the shift control switch is currently requesting.

Encoder Circuit A: The scan tool displays On or Off. This parameter indicates whether the transfer case shift control module is sensing voltage on the Encoder Circuit A. The scan tool displays On when the transfer case shift control module senses voltage less than or equal to 1 Volt. The scan tool displays Off when the transfer case shift control module senses voltage greater than or equal to 3 volts.

Encoder Circuit B: The scan tool displays On or Off. This parameter indicates whether the transfer case shift control module is sensing voltage on the Encoder Circuit B. The scan tool displays On when the transfer case shift control module senses voltage less than or equal to 1 Volt. The scan tool displays Off when the transfer case shift control module senses voltage greater than or equal to 3 volts.

Encoder Circuit C: The scan tool displays On or Off. This parameter indicates whether the transfer case shift control module is sensing voltage on the Encoder Circuit C. The scan tool displays On when the transfer case shift control module senses voltage less than or equal to 1 Volt. The scan tool displays Off when the transfer case shift control module senses voltage greater than or equal to 3 volts.

Encoder Circuit P: The scan tool displays On or Off. This parameter indicates whether the transfer case shift control module is sensing voltage on the Encoder Circuit P. The scan tool displays On when the transfer case shift control module senses voltage less than or equal to 1 Volt. The scan tool displays Off when the transfer case shift control module senses voltage greater than or equal to 3 volts.

Encoder Gear Position: The scan tool displays the mode the transfer case is currently in.

Front Axle Requested: The scan tool displays Yes or No. This parameter indicates Yes if the transfer case shift control module requests the front axle switch On.

Front Axle Switch: The scan tool displays Locked or Unlocked. This parameter indicates the feedback states of the front propshaft.

Front Propshaft Speed: The scan tool displays a range of 0-8,192 RPM. This parameter indicates the rotational speed of the front propshaft.

GM Part Number: The scan tool displays an eight-digit number. This parameter indicates the transfer case shift control module GM software number.

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

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

Mode Switch Selected: The scan tool displays the current mode selected. This parameter indicates the transfer case shift control switch button currently depressed by the driver.

Neutral Indicator Light: The scan tool displays On or Off. This parameter indicates On when the transfer case shift control module commands the neutral indicator light On.

Park Switch: The scan tool displays Open or Closed. This parameter indicates the feedback states of the Park/Neutral Switch.

Rear Propshaft Speed: The scan tool displays a range of 0-8,192 RPM. This parameter indicates the rotational speed of the rear propshaft.

Rear Propshaft Slippage: The scan tool displays a range of 0-8,192 RPM. This parameter indicates the total slippage of the rear propshaft.

Service 4WD Lamp: The scan tool displays On or Off. This parameter indicates On if the transfer case shift control module commands the Service 4WD lamp, or message, On.

Slip Adapt Mode: The scan tool displays Enabled or Disabled. This parameter indicates if the transfer case shift control module is currently attempting to prevent front to rear propshaft slip.

Slip Adapt PWM: The scan tool displays a range of 0-100 percent. This parameter indicates the duty cycle applied to the transfer case encoder motor.

Throttle Anticipation Mode: The scan tool displays Enabled or Disabled. This parameter changes from Disabled to Enabled when the vehicle starts movement from a stop position, light-to-heavy throttle is applied, and is currently in AWD mode. Throttle Anticipation Mode helps eliminate the clunking sound normally associated with front axle engagement.

Total Slippage: The scan tool displays a range of 0-8,192 RPM. This parameter indicates the total slippage of both the front and rear propshafts.

TP Angle: The scan tool displays a range of 0-100 percent. The TP Angle is computed by the PCM from the TP sensor voltage. The TP Angle should read 0 percent at idle and 100 percent at Wide Open Throttle (WOT).

Transfer Case Lock: The scan tool displays Enabled or Disabled. This parameter indicates Enabled if the transfer case shift control module commands the transfer case motor brake On.