GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 233-NP1 (Two Speed Selectable) 🢒 One or Two Shift Select Buttons Do Not Light

Step

Action

Value(s)

Yes

No

1

Were you sent here from a diagnostic table?

Go to Step 2

Refer to Electric Shift Transfer Case Functional Test

2

Position the ignition switch to OFF for at least 6 seconds.

Position the ignition switch to RUN.

Can mode and range shifts be made?

Go to Step 3

Refer to Reduced or No Mode and Range Shift Operation

3
  1. If the 2H1 button will not light, check for and open on CKT 1563 between pin G on the shift select switch and pin C11 on the TCCM.
  2. If the 4H1 button will not light, check for an open on CKT 1566 between pin F on the shift select switch and pin C12 on the TCCM.
  3. If the 4L0 button will not light, check for an open on CKT 1565 between pin E on the shift select switch and pin C14 on the TCCM.

Is an open found on the CKT checked

Go to Step 4

Go to Step 5

4

Repair the open CKT.

Is the repair completed?

Refer to Electric Shift Transfer Case Functional Test

--

5
  1. If 2H1 does not light, check for B+ voltage at pin C11 on the TCCM.
  2. If 4H1 does not light, check for B+ voltage at pin C12 on the TCCM.
  3. If 4L0 does not light, check for B+ voltage at pin C14 on the TCCM.

Is B+ voltage at the checked pin?

Go to Step 8

Go to Step 6

6
  1. If 2H1 does not light, check for a open in CKT 1563 between pin G on the shift select switch and pin C11 on the TCCM.
  2. If 4H1 does not light, check for an open in CKT 1566 between pin F on the shift select switch and pin C12 on the TCCM.
  3. If 4L0 does not light, check for an open in CKT 1565 between pin E on the shift select switch and pin C14 on the TCCM.

Is the checked CKT open?

Go to Step 7

Go to Step 8

7
  1. Position the ignition switch to OFF.
  2. Repair the open in the CKT.

Is the repair completed?

Refer to Electric Shift Transfer Case Functional Test

--

8
  1. Position the ignition switch to OFF.
  2. If 2H1 does not light, position a jumper from pin C11 to a vehicle ground source.
  3. If 4H1 does not light, position a jumper from pin C12 to a vehicle ground source.
  4. If 4L0 does not light, position a jumper from pin C14 to a vehicle ground source.
  5. Position the ignition switch to RUN.

Does the shift select button light?

Refer to Perform a Diagnostic On the TCCM

Go to Step 9

9

Replace the shift select switch.

Has the switch been replaced?

Refer to Electric Shift Transfer Case Functional Test

--