GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 Envoy - 4WD 🢒 DTC 🢒 DTC C0327

Circuit Description

The transfer case encoder is an analog sensor that returns a signal that represents the physical position of the transfer case sector shaft. The signal represents the mode or position that the transfer case is currently in.

This sensor is made up of the following 3 circuits:

    • A 5 volt reference circuit
    • An encoder signal circuit
    • An encoder low reference circuit

This DTC detects an out of range reading from the encoder signal or a short to voltage on the 5 volt reference circuit.

Conditions for Setting the DTC

The transfer case shift control module has a predefined range in which the encoder feed back should stay within, 0.5-4.5 volts. The DTC sets if the encoder signal feed back falls out of this range.

Action Taken When the DTC Sets
    • All motor activity stops.
    • The SERVICE AWD 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 no longer exists.
    • A history DTC clears after 100 consecutive ignition cycles without a fault present.
    • History DTCs can be cleared using a scan tool.

Diagnostic Aid

Check the mechanical condition of the shift lever detent shaft connected to the motor. If this shaft has too much mechanical play this can cause an under voltage or over voltage from the encoder causing the DTC to set.

Test Description

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

  1. This step tests the encoder circuit for a current malfunction.

    2.

  2. This step tests for proper reference voltage at the encoder.

    3.

  3. This step tests the 5 volt reference encoder circuit for a short to voltage, short to ground, an open or high resistance.

    4.

  4. After determining that the reference voltage measured in Step 4 was correct, Step 6 reviews the reading originally measured in Step 3 to see if it was higher or lower than what is expected. This step helps determine whether the Encoder Signal circuit is being pulled high or low.

    5.

  5. This step tests the encoder signal circuit and the encoder low reference circuit for a short to voltage.

    6.

  6. This step helps determine a faulty encoder.

    7.

  7. This step tests the encoder signal circuit for an open or a short to ground.

    8.

  8. This step tests the encoder low reference circuit for an open or high resistance.

Step

Action

Value(s)

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?

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Go to Step 2

Go to Diagnostic System Check - Transfer Case

2

  1. Install a scan tool.
  2. Start the engine.
  3. Place the transmission in NEUTRAL.
  4. Set the parking brake.
  5. With a scan tool, observe the Encoder Return Voltage Parameter in the Transfer Case Data List.

Does the voltage reading stay within the specified values?

0.5-4.5 V

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

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. Measure the voltage from the 5 volt reference encoder circuit to a good ground.

Does the voltage measure within the specified values?

4.8-5.2 V

Go to Step 5

Go to Step 4

4

Test the 5 volt reference encoder circuit for a short to voltage, short to ground, an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found and corrected?

--

Go to Step 12

Go to Step 11

5

Was the voltage reading measured in Step 3 greater than 5.2 volts?

--

Go to Step 6

Go to Step 7

6

Test the encoder signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found and corrected?

--

Go to Step 12

Go to Step 11

7

  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With the encoder connector disconnected, use a fused jumper and probe between the 5 volt reference encoder circuit and encoder signal circuit.
  4. With a scan tool, observe the Encoder Return Voltage Parameter in the Transfer Case Data List.

Is the Encoder Return Voltage display within the specified values?

4.8-5.2 V

Go to Step 9

Go to Step 8

8

Test the encoder signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Was the condition found and corrected?

--

Go to Step 12

Go to Step 11

9

Test the encoder low reference circuit for an open or high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

10

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

Did you complete the repair?

--

Go to Step 12

--

11

Important: After transfer case shift control module replacement and reprogramming, ensure all doors are closed and the key is out of the ignition, then open and close the doors again and wait 2 minutes to avoid incomplete programming or setting false communication DTCs.

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

Did you complete the repair?

--

Go to Step 12

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12
  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