GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Blazer - 4WD 🢒 DTC 🢒 DTC C0376

Circuit Description

The front and rear propshaft speed sensor is a permanent magnet (PM) generator. The PM generator produces a pulsing AC voltage. The AC voltage level and number of pulses increases as speed increases. The module converts the pulsating AC voltage to a propshaft RPM, which is used for calculations. The module looks at these inputs together when the vehicle is in 4H, 4L, and AUTO 4WD range only. The propshaft RPM can be displayed with a scan tool.

This DTC detects greater than 10 percent difference in the speed sensor inputs.

Conditions for Running the DTC
    • The ignition is ON.
    • System voltage is 9-16 volts.

Conditions for Setting the DTC

The transfer case shift control module detects continued readings of front and rear propshaft speed signal which do not match. The module is unable to determine propshaft speed.

The system logs the DTC if the front and rear propshaft inputs indicates a speed greater than 10 percent difference for 40 seconds, while all of the following are true:

    • The transmission is NOT in PARK/NEUTRAL.
    • The engine is running.
    • The front axle is engaged.
    • The front propshaft indicates speed less than 120 km/h (75 mph).
    • The front propshaft or rear propshaft speed exceeds 512 RPM.
    • Vehicle Speed On Class 2 Data bus exceeds 16 km/h (10 mph).

Action Taken When the DTC Sets
    • All shifts to AUTO 4WD mode is disabled. If the current mode is AUTO 4WD, the system will not allow any further adaptive events, correct wheel slip.
    • The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC
    • The transfer case shift control module clears the DTC if the condition for setting the DTC does not exist.
    • A history DTC clears after 100 consecutive ignition cycles without a fault present.
    • History DTCs can be cleared using a scan tool.

Test Description

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

  1. This step helps determine if the transfer case speed sensors are operating properly.

    2.

  2. This step tests to see if the DTC will set.

    3.

  3. This step inspects for mismatches and whether speed sensors are wired correctly.

    4.

  4. This step inspects the transfer case for mechanical failures.

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

Connector End View Reference: Transfer Case Control Connector End Views

1

Did you perform the Diagnostic System Check - Transfer Case?

Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

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

Go to DTC C0300 or DTC C0305

Go to Step 3

3

  1. Clear all ATC DTCs.
  2. Place the transfer case into 4WD mode.
  3. Install a scan tool.
  4. Monitor both the front and rear propshaft speed sensors while driving the vehicle.

Are both propshaft speed sensors within 10 percent of each other?

Go to Step 4

Go to Step 5

4

Does DTC C0376 set?

Go to Step 7

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

5

  1. Turn the ignition OFF.
  2. Inspect the following for a mismatch:
    3. • Front and rear axle ratios
    • All tires
    • Front or rear propshaft missing
  3. Inspect that the speed sensors are wired correctly, by comparing the vehicle wire harness to the system schematics. Inspect the connectors for proper connection and for loose terminals.

Did you find and correct the condition?

Go to Step 8

Go to Step 6

6

Inspect the transfer case for a mechanical failure.

Has a mechanical failure been identified and repaired?

Go to Step 8

Go to Step 7

7

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

Did you complete the repair?

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 set?

Go to Step 2

System OK