GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 Jimmy - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 233-NP1 🢒 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.

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. A scan tool cannot be utilized on this transfer case.

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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 in Wiring Systems

Go to Step 3

3

Use the scan tool in order to observe the Vehicle Speed Sensor parameter on the transmission Scan Tool Data Lists.

Is the vehicle speed the specified value?

0 km/h (0 mph)

Go to Step 4

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

4

  1. Place the transmission in Neutral.
  2. Ensure that the transmission is in Neutral and the clutch pedal is depressed on a manual transmission, or using the scan tool observe the TR Sw. parameter in the automatic transmission Scan Tool Data List.

Does the scan tool indicate the transmission is in Neutral, or that the clutch pedal is depressed?

--

Go to Step 5

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

5

Replace the TCCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 6

--

6

Operate the vehicle in order to determine if the symptom has been corrected.

Is the symptom still present?

--

Go to Step 2

System OK