GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Pickup - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 243-NP1 (Two Speed Selectable) 🢒 Diagnostic System Check

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.

    2.

  2. Perform diagnostics for powertrain DTC's first before addressing other DTC's. They can be responsible for setting other DTC's.

    3.

  3. The presence of DTC's indicates that the transfer case shift control module has detected a fault. Go to symptoms for other concerns.

Step

Action

Yes

No

1

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Inoperative in Data Link Communications

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to establish communication with the powertrain control module.

Does the scan tool communicate with the powertrain control module?

Go to Step 3

Go to Scan Tool Does Not Communicate with Class 2 Data Line in Data Link Communications

3

Select the powertrain control module display DTCs function on the scan tool.

Does the scan tool display any DTCs?

Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 5.0L and 5.7L, Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 6.5L, or Powertrain On Board Diagnostic (OBD) System Check in Engine Controls - 7.4L

Go to Step 4

4

Check the transfer case shift control module for DTC's. The transfer case shift control module is not a class 2 device. DTC's are displayed on the transfer case shift control switch. Refer to Diagnostic Trouble Code (DTC) Displaying .

Are any DTC's present?

Go to Diagnostic Trouble Code (DTC) List

Go to Symptoms - Transfer Case