GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 236/246-NP8 (Two Speed Automatic) 🢒 DTC C0374

Circuit Description

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

Action Taken When DTC Sets

All transfer case shift is disabled while DTC is present and current.

Conditions for Setting the DTC

The transfer case shift control module is unable to correct sensed slip for 10 consecutive seconds.

Conditions for Clearing the DTC
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • Use a scan tool in order to clear history and current DTCs.

Test Description

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

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

    2.

  2. Tests the integrity of the Motor Control circuit.

    3.

  3. Determines whether the Encoder Motor is moving to the proper position.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: If DTC C0300 or C0305 is also present perform the diagnostic for these DTCs before continuing.

Did you perform the Transfer Case Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

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

Is the Encoder Motor turning ON, or is there a buzzing noise?

Go to Step 4

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the encoder motor.
  3. Turn the ignition ON, with the engine OFF.
  4. Cycle the transfer case between 2WD and 4WD.
  5. Use the scan tool to check for DTCs.

Did DTC C0310 set?

Go to Step 6

Go to Step 7

4

  1. Using the scan tool device control for the ATC Mode Switch, manually command the transfer case gear positions.
  2. Use the Increase and Decrease buttons on the scan tool to command through all the ATC Mode Switch states while observing the Encoder Gear Position parameter.

Does the Encoder Gear Position parameter state change as commanded by the scan tool?

Go to Step 5

Go to Step 6

5

Remove the transfer case and overhaul.

Is the repair complete?

Go to Step 8

--

6

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

Is the repair complete?

Go to Step 8

--

7

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

Is the repair complete?

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK