GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Astro - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 136-NP4 🢒 Transfer Case Will Not Correct Slip

Circuit Description

The transfer case shift control module senses rear to front slip, a difference of rear to front wheel speed, attempts to correct the difference by activating the encoder motor, to apply more torque to the front wheels.

Test Description

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

  1. Determines if the transfer case shift control module is setting DTCs C0300 or C0305.

    2.

  2. Helps determine if the DTC set due to a mechanical or an electrical fault.

    3.

  3. Tests the integrity of the Motor Control circuit.

    4.

  4. Determines whether the transfer case clutch pack is holding.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Did you peform the Diagnostic System Check - Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

Had the transfer case shift control module set C0300 or C0305 as a current DTC?

Go to DTC C0300 or DTC C0305

Go to Step 3

3

  1. Place the transmission in PARK
  2. Turn the ignition ON, with the engine OFF.
  3. Install a scan tool.
  4. Use the scan tool in order to command the Encoder Motor B ON.

Is the Encoder Motor turning ON?

Go to Step 5

Go to Step 4

4

  1. Turn the ignition OFF.
  2. Disconnect the encoder motor harness.
  3. Turn the ignition ON, with the engine OFF.
  4. Use the scan tool to check for DTCs.

Did DTC C0310 set?

Go to Step 7

Go to Step 8

5

  1. Remove the encoder motor assembly. Refer to Transfer Case Motor/Encoder Replacement .
  2. Connect a wrench to the transfer case sector shaft.
  3. Turn the sector shaft to apply the clutch pack.
  4. While the clutch pack is applied, attempt to turn the front propshaft using a small pry bar between the U-Joint.

Does the clutch pack hold the propshaft and prevent it from being turned?

Go to Step 7

Go to Step 6

6

Remove the transfer case and overhaul.

Did you complete the repair?

Go to Step 9

--

7

Replace the transfer case encoder motor. Refer to Transfer Case Motor/Encoder Replacement .

Did you complete the repair?

Go to Step 9

--

8

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

Did you complete the repair?

Go to Step 9

--

9
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for allowing the symptom to re-occur.

Does the DTC reset?

Go to Step 2

System OK