GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 GMC K Pickup - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 243-NP1 (Two Speed Selectable) 🢒 Transfer Case Shift Control Switch Inoperative

Circuit Description

The transfer case shift control switch circuit consists of three normally open switches. From the GAUGES fuse the switch is supplied with ignition 1 voltage. When one of the switches is pressed, current travels through the normally open switch to the corresponding circuit (2 'HI', 4 'HI', or 4'LO' Selector Switch Signal) and to the transfer case shift control module. The transfer case shift control module continuously monitors the switch inputs to determine whether the 2HI, 4HI, or 4LO buttons have been selected by the driver.

Test Description

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

  1. This step tests the functionality of the transfer case shift control switch buttons.

    2.

  2. This step tests the transfer case shift control switch for proper function.

    3.

  3. This step tests the individual selector switch circuits.

    4.

  4. This step tests the transfer case shift control switch ignition 1 circuit for proper voltage.

    5.

  5. This step tests the transfer case shift control switch for proper function.

    6.

  6. This step tests the park signal circuit for proper voltage.

    7.

  7. This step repairs an open or high resistance in the park signal circuit.

    8.

  8. This step tests the suspect selector switch signal circuit for an open or high resistance.

    9.

  9. This step tests the 4WD fuse for an open.

    10.

  10. This step repairs an open in the transfer case shift control switch ignition 1 voltage circuit.

    11.

  11. This step tests the 4WD fuse to determine if it re-blows.

    12.

  12. The step tests the transfer case shift control switch ignition 1 voltage circuit and the selector switch signal circuits for a short to ground.

Transfer Case Shift Control Switch Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform A 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.
  3. Set the park brake.
  4. Depress each of the shift control switch buttons.

Are all of the buttons on the shift control switch working properly?

--

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

Go to Step 3

3

Is only one button on the shift control switch inoperative?

--

Go to Step 4

Go to Step 5

4

  1. Turn ON the ignition with the engine OFF.
  2. Connect one end of a DMM to ground.
  3. At the back of the shift control switch, back probe the suspect selector switch signal circuit while pressing it's corresponding switch.

Was the voltage within the specified value?

B+

Go to Step 9

Go to Step 14

5

  1. Turn ON the ignition, with the engine OFF.
  2. Test the shift control switch ignition 1 voltage circuit for proper voltage.

Was the voltage within the specified value?

B+

Go to Step 6

Go to Step 10

6

  1. Connect one lead of a DMM to ground.
  2. At the back of the shift control switch, back probe each of the signal circuits while pressing their corresponding switch.

Was the voltage within the specified value for each of the circuits?

B+

Go to Step 7

Go to Step 14

7

  1. Turn OFF the ignition.
  2. Disconnect the connectors at the transfer case shift control module.
  3. Connect one lead of a DMM to ground.
  4. At the harness side of the transfer case shift control module connector, connect the other lead of the DMM to the park signal circuit.
  5. Turn ON the ignition, with the engine OFF.
  6. With the vehicle in Park, measure the voltage at the park signal circuit.

Was the voltage within the specified value?

B+

Go to Step 15

Go to Step 8

8

Test for an open or high resistance in the park signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

--

9

  1. Turn OFF the ignition.
  2. Test the suspect selector switch signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

10

Test the 4WD fuse for an open.

was the fuse open?

--

Go to Step 12

Go to Step 11

11

Repair an open in the shift control switch ignition 1 voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

12

  1. Replace the 4WD fuse.
  2. Take the vehicle for a test drive.
  3. Place the transmission into NEUTRAL.
  4. Set the park brake.
  5. Press each of the shift control switch buttons.
  6. Retest the 4WD fuse for an open.

Did the fuse blow again?

--

Go to Step 13

Go to Step 16

13

Test the shift control switch ignition 1 voltage circuit and the selector switch signal circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 16

--

14

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

Did you complete the replacement?

--

Go to Step 16

--

15

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

Did you complete the replacement?

--

Go to Step 16

--

16

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