GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy K Silverado - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 246-NP8 (Two Speed Automatic) 🢒 DTC C0374 General System Malfunction

Circuit Description

The Auto Transfer Case (ATC) Control Module senses rear to front slip, a difference of rear to front wheel speed, attempts to correct the difference by turning on the motor, internal to the Transfer Case, to apply torque to the front wheels.

Conditions for Setting the DTC

The Auto Transfer Case (ATC) 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 number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks to see if the transfer case shift control module has electronic control of the encoder motor.

    2.

  2. This step checks to see if the transfer case shift control module can sense whether or not the encoder motor is connected.

    3.

  3. This step determines if the encoder is moving to the correct gear positions.

Step

Action

Value(s)

Yes

No

1

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

Was the Transfer Case Diagnostic System Check performed?

--

Go to Step 2

Go to Transfer Case Diagnostic System Check

2

  1. Place transmission in PARK.
  2. Turn the Ignition to the RUN position.
  3. Connect the Scan Tool .
  4. Use the Scan Tool to command Encoder Motor A and Encoder Motor B On.

Is the encoder motor turning on (buzzing noise)?

--

Go to Step 5

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the wire harness at the encoder motor.
  3. Turn the ignition switch to RUN.
  4. Use the Scan Tool to check for DTCs.

Did DTC C0310 set?

--

Go to Step 7

Go to Step 4

4

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

Has the transfer case shift control module been replaced?

--

Go to Step 8

--

5

  1. Using the Scan Tool manually command gear position by using the device control for the ATC Mode Switch.
  2. Use the Increase and Decrease buttons on the scan tool to command through all the Mode Switch states while observing Encoder Gear Position.

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

--

Go to Step 6

Go to Step 7

6

Remove transfer case and overhaul. Refer to Transfer Case - New Venture Gear 246 in the Transfer Case Unit Repair Manual.

Are the repairs complete?

--

Go to Step 8

--

7

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

Is the repair complete?

--

Go to Step 8

--

8

Clear all ATC DTCs.

Have all the ATC DTCs been cleared?

--

Go to Transfer Case Diagnostic System Check

--