GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 233-NP1 (Two Speed Selectable) 🢒 Transfer Case Shift Control Switch Indicator Inoperative - One or More

Circuit Description

The indicator lamps circuit consists of 3 individual lamps contained inside respective buttons. This assembly is the transfer case shift-control switch, with the following indicators:

    • 2HI
    • 4HI
    • 4LO

When the ignition switch is placed in the RUN position, current is provided to the switch assembly. The transfer case shift control module provides a ground for the indicators when a particular gear is active or when the transfer case is in transition. Through solid state circuity located inside the switch assembly voltage can be regulated to provide less illumination when the headlamps or parking lights are turned ON.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step helps to determine intermittent conditions.

    2.

  2. This step helps to determine if the transfer case range changes with the press of all of the transfer case shift control switch buttons.

    3.

  3. This step determines if there is a faulty indicator inside the transfer case shift control switch assembly.

    4.

  4. This step repairs an open in the suspect indicator control circuit.

Switch Indicator Lamps Do Not Light - One or More

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: The transfer case shift control module is not a class 2 device, and therefore a scan tool can not be utilized on this transfer case.

Did you perform the Diagnostic System Check-Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

  1. Start the engine.
  2. Place the transmission into NEUTRAL, or depress the clutch pedal on manual transmission applications.
  3. Set the park brake.
  4. Press each of the shift control switch buttons.

Do the transfer case shift control switch indicator lamps illuminate with the press of all of the shift control switch buttons?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Determine if the transfer case range changes with the press of all of the shift control switch buttons

Does the transfer case range change with the press of all of the shift control switch buttons?

Go to Step 4

Go to Transfer Case Shift Control Switch Inoperative or 4 Low Indicator Stuck On

4

  1. Turn OFF the ignition.
  2. Remove the shift control switch in order to access the back of the switch, leaving the connectors still attached. Refer to Transfer Case Shift Control Switch Replacement .
  3. Turn ON the ignition.
  4. Connect one end of a fused jumper to a good ground and with the other end back probe each of the switch indicator control circuits.

Do the transfer case shift control switch indicator lamps turn ON when their specific control circuit is jumped to ground?

Go to Step 5

Go to Step 6

5

Repair an open in the suspect control circuits. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 8

Go to Step 7

6

Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement .

Did you complete the replacement?

Go to Step 8

--

7

Replace the transfer case control module. Refer to Transfer Case Shift Control Module Replacement .

Did you complete the replacement?

Go to Step 8

--

8

Operate the vehicle within the conditions for causing the symptom as specified in the supporting text.

Does the symptom re-occur?

Go to Step 2

System OK