GM Service Manual Online
For 1990-2009 cars only

The scan tool provides the following capabilities:

    • Displays the data list.
    • Displays current and history trouble codes.
    • Clear the diagnostic trouble codes after a repair is completed.

Important: Make sure the scan tool that you are using is functioning properly and has the latest software. Use of a malfunctioning scan tool or one that has old software can result in misdiagnosis and unnecessary parts replacement.

To use the scan tool, connect it to the Data Link Connector (DLC) and turn the ignition switch to the RUN position.

The Transfer Case Scan Tool Data List contains all the automatic transfer case (ATC) related parameters that are available on the scan tool. The scan tool data list is arranged in alphanumeric order.

Use the Transfer Case Scan Tool Data List only after the following is determined:

    • A Diagnostic System Check has been completed.
    • No Diagnostic Trouble Codes (DTCs) are set.
    • Transfer case diagnostic tables indicate the system is functioning properly.

Scan tool values from a properly operating system may be used for comparison with the transfer case system you are diagnosing. The Transfer Case Scan Tool Data List represents values recorded under the following conditions:

    • Engine is at idle
    • Closed throttle
    • Gear is in PARK or NEUTRAL
    • Accessories are OFF

Only the parameters listed below are referenced in this service manual for use in diagnosis. If all values are within the typical range described below, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for further diagnosis.

Scan Tool Parameter

Data List

Units Displayed

Typical Data Value

Engine is at Idle, Upper Radiator Hose Hot, Closed Throttle, Gear is in Park or Neutral, and Accessories are OFF.

2WD High Indicator Light

Data Display

On/Off

Off

4WD High Indicator Light

Data Display

On/Off

Off

4WD Low Indicator Light

Data Display

On/Off

Off

ATC Slip Speed

Data Display

RPM

0

Auto 4WD Indicator Light

Data Display

On/Off

On

Commanded Mode Indicator

Data Display

2WD/4WD High/4WD Low/Auto 4WD

Varies

Encoder Circuit A

Data Display

On/Off

Off

Encoder Circuit B

Data Display

On/Off

On

Encoder Circuit C

Data Display

On/Off

Off

Encoder Circuit P

Data Display

On/Off

On

Encoder Gear Position

Data Display

2WD/4WD High/4WD Low/Auto 4WD

Varies

Front Axle Requested

Data Display

Yes/No

Yes

Front Axle Switch

Data Display

Locked/Unlocked

Locked

Front Propshaft Speed

Data Display

RPM

0

Ignition 3

Data Display

Volts

Battery Voltage

Last Adapt Highest PWM

Data Display

% DC

0

Mode Switch Selected

Data Display

On/Off

Off

Neutral Indicator Light

Data Display

On/Off

Off

Park Switch

Data Display

Closed/Open

Closed

Rear Propshaft Speed

Data Display

RPM

0

Rear Slippage

Data Display

RPM

0

Service 4WD Lamp

Data Display

On/Off

Off

Service 4WD Lamp Open

Data Display

Yes/No

No

Service 4WD Lamp Shorted

Data Display

Yes/No

No

Slip Adapt Mode

Data Display

Enabled/Disabled

Disabled

Slip Adapt PWM

Data Display

% DC

0

Throttle Anticipation Mode

Data Display

Enabled/Disabled

Disabled

Total Slippage

Data Display

RPM

0

TP Angle

Data Display

%

0

Transfer Case Lock

Data Display

Enabled/Disabled

Enabled