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Home >> Chevrolet >> 2016 >> Suburban 3500 HD LT >> Repair and Diagnosis >> Transmission >> Transfer Case >> Transfer Case - Mp 3023/3024 (NQH) - Diagnostic Information And Procedures >> Diagnostic Information and Procedures >> DTC C0321 or C0326: Range Actuator Lock Control >> Circuit/System Testing

Circuit/System Testing

  1. Verify that the 4WD TREC fuse, X50A Fuse Block - Underhood fuse 6, and the Accessory/Run Crank fuse, X51L Fuse Block - Instrument Panel Left - fuse 31, are not open.
    • If the 4WD TREC fuse is open 

      Test the battery positive voltage, K69 transfer case control module harness X3 terminal C, for a short to ground.

    • If the Accessory/Run Crank fuse is open 

      Test the Accessory/Run Crank voltage circuit, K69 transfer case control module harness X2 terminal 4, for a short to ground.

    • If neither fuse is open 
  2. Ignition ON, engine OFF.
  3. Disconnect the harness connector at the A16 transfer case range actuator.
    4. NOTE:
    • When test probing harness terminals, it is imperative to use the proper test probe from the most current version of the J 35616  Kit. Use of an improper test probe may deform the terminal, resulting in intermittent open conditions.
    • Testing for steps 3-5 is performed on the A16 transfer case motor harness connector using the PU probes J 35616-4A.
  4. Test for B+ (+0.0/-1.0 V) between the battery positive voltage circuit, A16 transfer case range actuator harness terminal B, and a good ground.
    • If the voltage is less than B+ (+0.0/-1.0 V) 
    1. Ignition OFF, disconnect the X2 harness connector at the X50A Fuse Block - Underhood.
    2. Test for less than 10 Ω in battery positive voltage circuit end to end.
      • If 10 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 10 Ω 
    3. Test for infinite resistance between battery positive voltage circuit and a good ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. Test for infinite resistance between the battery positive voltage circuit, A16 transfer case motor harness terminal B, and all other terminals of the A16 transfer case motor harness connector.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the K69 transfer case control module and perform the Range Actuator Learn procedure. The Range Actuator Learn procedure is also known as the Transfer Case High/Low Clutch Reset procedure.

        Refer to Transfer Case Control Module Replacement .

    • If the voltage is B+ (+0.0/-1.0 V) 
  5. Test for a 4.0-5.0 V diagnostic voltage between the transfer case lock solenoid control circuit, A16 Transfer Case Motor terminal C, and a good ground.
    • If the voltage is greater than the specified range 
    1. Ignition OFF, disconnect the X1 harness connector at the K69 transfer case control module.
    2. Ignition ON, engine OFF.
    3. Test for less than 1 V between the transfer case lock solenoid control circuit and a good ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    4. Test for infinite resistance between the transfer case lock solenoid control circuit, A16 transfer case motor harness connector terminal C and all other terminals of the A16 transfer case motor harness connector.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the K69 transfer case control module and perform the Range Actuator Learn procedure. The Range Actuator Learn procedure is also known as the Transfer Case High/Low Clutch Reset procedure.

        Refer to Transfer Case Control Module Replacement .

    • If the voltage is less than the specified range 
    1. Ignition OFF, disconnect the X1 harness connector at the K69 transfer case control module.
    2. Test for less than 10 Ω in the transfer case lock solenoid control circuit end to end.
      • If 10 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 10 Ω
    3. Test for infinite resistance transfer case lock solenoid control circuit, A16 transfer case motor harness connector terminal C and a good ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. Test for infinite resistance between the transfer case lock solenoid control circuit, A16 transfer case motor harness connector terminal C and all other terminals of the A16 transfer case motor harness connector.
      • If less than infinite resistance, repair the shorted together condition in the affected circuits.
      • If infinite resistance, replace the K69 transfer case control module and perform the Range Actuator Learn procedure. The Range Actuator Learn procedure is also known as the Transfer Case High/Low Clutch Reset procedure.

        Refer to Transfer Case Control Module Replacement .

    • If the voltage is within the specified range 
  6. Battery Positive Voltage circuit and Transfer Case Lock Solenoid Control circuit OK.
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