GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Blazer - 2WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 233-NP1 (Two Speed Selectable) 🢒 Transfer Case Shift Control Switch Indicator Flashes and Returns to Original Mode

Circuit Description

This symptom usually occurs when a shift into or out of 4LOW will not occur. When the transfer case control module (TCCM) receives a request to shift into or out of 4LOW, the TCCM must see the following parameters before the shift routine can start:

    • The vehicle speed must be below 3 MPH.
    • The transmission must be in neutral.

If the TCCM does not see these conditions the shift control switch indicator lamp will flash for approximately 5 seconds and then return to the original gear.

Test Description

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

  1. This step tests the operation of the transfer case shift control switch to help determine if the system is operating properly.

    2.

  2. This step determines if the vehicle speed sensor reading is correct.

    3.

  3. This step determines if the park switch reading is correct.

Switch Indicator Lamp Flashes and Returns to Original Mode

Step

Action

Value(s)

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 A Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

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.

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

--

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Use the scan tool in order to read the vehicle speed sensor on the transmission control Data Lists.

Is the vehicle speed within the specified range?

0 km/h (0 mph)

Go to Step 4

Go to Powertrain On Board Diagnostic (OBD) System Check for the 4.3L engine

4

  1. Put the transmission in neutral.
  2. Observe the current state of the transmission on the scan tool in the transmission control Data 2 List.

Does the scan tool indicate the transmission is in Neutral?

--

Go to Step 5

Go to Powertrain On Board Diagnostic (OBD) System Check for the 4.3L engine

5

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

Did you complete the replacement?

--

Go to Step 6

--

6

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