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MP 3010-NP0 - Transfer Case




DTC C0306

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.

DTC Descriptors
DTC C0306 02
- Motor A or B Circuit Short to Ground

DTC C0306 05
- Motor A or B Circuit Short to Battery or Open

Diagnostic Fault Information






Circuit/System Description

The transfer case encoder motor (TCEM) is a bi-directional, permanent magnet, DC motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module (TCCM) ground circuit, the TCEM, through a series of gears, rotates the transfer case control actuator shaft which moves the transfer case two/four wheel drive actuator cam and transfer case high/low shift fork to shift the transfer case between the following modes or ranges:

* 2WD HI
* 4WD Auto
* 4WD HI

Conditions for Running the DTC

* Ignition ON
* System voltage 10.5-18 V

Conditions for Setting the DTC

* The TCCM tests the motor circuits by checking for unexpected voltage.
* The TCCM supplies voltage on each of the motor circuits and reads the voltage back on the other circuit.
* If the TCCM detects a low voltage return when a high voltage is expected, or a high voltage return when a low voltage is expected, the DTC is logged.
* The fault must remain current for 1 second to set the DTC.

Action Taken When the DTC Sets

* All shifting is disabled.
* The mode light shall flash upon a requested mode change and then return to the current mode.
* The SERVICE 4WD indicator remains illuminated for the remainder of the current ignition cycle.

Conditions for Clearing the DTC

* The TCCM clears the DTC once the conditions for setting the DTC are no longer present.
* A history DTC clears after 40 consecutive warm-up cycles without a fault present.
* History DTCs can be cleared using a scan tool.

Diagnostic Aids

* It is possible to have windings inside the motor shorted to the case, resulting in a short to ground, causing this DTC to set.
* The default actions for C0321 may set C0306.
* EL-49741 - harness is a good source for 9 V.
* EL-49742 - harness is a good source for B+ and ground.
* The transfer case fill and drain plugs are a good source for ground.

Reference Information
Schematic Reference

Transfer Case Control Schematics MP 3010-NP0 - Transfer Case
Connector End View Reference

Component Connector End Views Connector End Views By Name
Electrical Information Reference

* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Programming and Relearningfor scan tool information
Special Tools

* EL-49741 - 9 V+ Power Source Harness
* EL-49742 - Battery Voltage B+ and Ground Source Harness
* J 35616 - GM-Approved Terminal Test Kit

Circuit/System Testing

1. Verify that the TREC fuse, and the miscellaneous IGN fuse, underhood fuse block, are not open.

• If the TREC fuse is open, test the battery positive voltage, TCCM Harness X3 pin C, for a short to ground.
• If the miscellaneous IGN fuse is open, test the ignition 1 voltage circuit, TCCM Harness X2 pin 6, for a short to ground.

2. Ignition ON, engine OFF.
3. With a scan tool, check DTC's. If DTC C0321 is set, go to C0321.
4. Disconnect the X1 harness connector at the transfer case encoder motor (TCEM).

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.

5. Using the purple probe J 35616-4A, test for a 1.0-2.5 V diagnostic voltage between the motor B circuit, TCEM X1 pin D, and a good ground.

• If the voltage is greater than the specified range, test the motor B circuit for a short to voltage. If all circuits and connections test normal, test the TCCM.
• If the voltage is less than the specified range, test the motor B circuit for an open/high resistance or short to ground. If all circuits and connections test normal, test the TCCM.

6. Using the purple probes J 35616-4A, test for a diagnostic B+ (+0.0/-1.0 V) between the motor A circuit, TCEM harness X1 pin A, and a good ground.

• If the voltage is less than the specified range, test the motor A circuit for an open/high resistance, short to ground or short together condition. If all circuits and connections test normal, test the TCCM.

7. Remove the encoder motor from transfer case. Using a paint pen or marker, place indexing marks on the encoder motor output gear and the mounting surface of the encoder motor.
8. Connect the X1 connector at the transfer case encoder motor (TCEM). Position the TCEM so that the indexing marks are visible from the side of the vehicle.
9. Remove key. Wait 30 seconds. Key ON, engine OFF. Clear codes.
10. Block wheels. Parking brake engaged. Transmission in Neutral. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the encoder motor forward and reverse. When commanded forward, the encoder motor drive gear should rotate in one direction. When commanded reverse, the encoder motor drive gear should rotate in the opposite direction.

• If the encoder motor drive gear is unable to rotate, test the TCEM.

11. Inspect the transfer case actuator shaft gear for a binding condition. If binding, remove the transfer case and repair the binding condition.
12. Test the TCEM.

Component Testing

Transfer Case Encoder Motor (TCEM) - Actuator Lock, Motor A and Motor B
1. Remove the encoder motor from transfer case. Using a paint pen or marker, place indexing marks on the encoder motor drive gear and the mounting surface of the encoder motor.
2. Using a purple probe J-35616-5, attach the red lead from one of the EL-49741 - harnesses to the battery positive voltage terminal of the TCEM, pin B.
3. Using a purple probe J-35616-5, attach the black lead from this same jumper harness to the lock solenoid control terminal of the TCEM, pin C.
4. Attach a 9 volt battery to this harness (not included). You will hear the encoder motor unlock.
5. Using a purple probe J-35616-5, attach the red lead from the other jumper EL-49741 - harness to the motor control A terminal of the TCEM, pin A.
6. Using a purple probe J-35616-5, attach the black lead from this same jumper harness to the motor control B terminal of the TCEM, pin D.
7. Touch the battery terminals of the 9 volt battery to the battery terminals of the jumper harness. This should rotate the encoder motor drive gear in either a clockwise or counter-clockwise rotation depending on battery orientation.

• If the encoder motor drive gear does not rotate, replace the encoder motor.

8. Using the purple probes J 35616-5, test for between 0.3-40 ohm between the motor control A circuit TCEM X1 pin A and the motor control B circuit TCEM X1 pin D.

• If greater than the specified range, replace the encoder motor.
• If less than the specified range, replace the encoder motor.

9. Using the purple probes J 35616-5, test for greater than 10 ohm between the following circuits and the encoder motor case:

* Motor control A, TCEM harness X1 pin A.
* Motor control B, TCEM harness X1 pin D.

• If outside the specified range, replace the encoder motor.

10. Using the purple probes J 35616-5, test for greater than 1 M ohm between the motor control A circuit, TCEM X1 pin A and all other pins on the TCEM harness X1 except the motor control B, TCEM X1 pin D.

• If outside the specified range, replace the encoder motor.

11. Using the purple probes J 35616-5, test for greater than 1 M ohm between the motor control B circuit, TCEM X1 pin D. and all other pins on the TCEM harness X1 except the motor control A circuit, TCEM X1 pin A.

• If outside the specified range, replace the encoder motor.

12. Test the TCCM.

TCCM
1. Ignition OFF. Disconnect the X1 harness connector at the TCEM.
2. Ignition ON, engine OFF. Install EL-49742 - harness.
3. Using the purple probes J 35616-4A, connect a test lamp between the motor control A circuit, TCEM X1 pin A and the ground terminal of EL-49742 - harness , black terminal.
4. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded forward, the test light should illuminate for 10 seconds and turn OFF. When commanded reverse, the test light should turn OFF.

• If the test light stays ON when commanded OFF, test the motor control A circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate when commanded ON, test the motor control A circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

5. Using the purple probes J 35616-4A, connect a test lamp between the motor control B circuit, TCEM X1 pin D and the ground terminal of EL-49742 - harness , black terminal.
6. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded forward, the test light should turn OFF. When commanded reverse, the test light should illuminate for 10 seconds and turn OFF.

• If the test light stays ON when commanded OFF, test the motor control B circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate when commanded ON, test the motor control B circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

7. Using the purple probes J 35616-4A, connect a test lamp between the motor control A circuit, TCEM X1 pin A and a good ground.
8. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded Forward/Counter CW, the test light should illuminate dimly for 10 seconds and turn OFF. When commanded Reverse/Clockwise, the test light should turn OFF.

• If the test light stays ON after the 10 seconds, test the motor control A circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate at all, test the motor control A circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

9. Using the purple probes J 35616-4A, connect a test lamp between the motor control B circuit, TCEM X1 pin D and a good ground.
10. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded Forward/Counter CW, the test light should turn OFF. When commanded Reverse/Clockwise, the test light should illuminate dimly for 10 seconds and turn OFF.

• If the test light stays ON after the 10 seconds, test the motor control B circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate at all, test the motor control B circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

11. Using the purple probes J 35616-4A, connect a test lamp between the motor control A circuit, TCEM X1 pin A and the B+ terminal of EL-49742 - harness , red terminal.
12. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded Forward/Counter CW, the test light should illuminate dimly for 10 seconds and turn OFF. When commanded Reverse/Clockwise, the test light should illuminate brightly for 10 seconds and turn OFF.

• If the test light stays ON after the 10 seconds, test the motor control A circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate at all, test the motor control A circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

13. Using the purple probes J 35616-4A, connect a test lamp between the motor control B circuit, TCEM X1 pin D and the B+ terminal of EL-49742 - harness , red terminal.
14. Using the Transfer Case Motor Control function of the Special Function feature of the scan tool, command the motor forward and reverse. When commanded Forward/Counter CW, the test light should illuminate brightly for 10 seconds and turn OFF. When commanded Reverse/Clockwise, the test light should illuminate dimly for 10 seconds and turn OFF.

• If the test light stays ON after the 10 seconds, test the motor control B circuit for a short to voltage. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.
• If the test light does not illuminate at all, test the motor control B circuit for an open or short to ground. If all circuits and connections test normal, reprogram the TCCM. If the DTC continues to set replace the TCCM.

15. Test the TCEM.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Control Module References Programming and Relearningfor TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset Transfer Case High/Low Clutch Reset
* Transfer Case Two/Four Wheel Drive Actuator Replacement Transfer Case Two/Four Wheel Drive Actuator Replacement
* Transfer Case Disassemble Transfer Case Disassemble
* Transfer Case Assemble Transfer Case Assemble
* Oil Pump Cleaning and Inspection Oil Pump Cleaning and Inspection
* Rear Output Shaft Cleaning and Inspection Rear Output Shaft Cleaning and Inspection
* Front Output Shaft and Input Shaft Cleaning and Inspection Front Output Shaft and Input Shaft Cleaning and Inspection
* Drive Chain, Drive Sprocket, and Driven Sprocket Cleaning and Inspection Drive Chain, Drive Sprocket, and Driven Sprocket Cleaning and Inspection
* High/Low Shift Components Cleaning and Inspection High/Low Shift Components Cleaning and Inspection
* Two/Four Wheel Drive Shift Components Cleaning and Inspection Two/Four Wheel Drive Shift Components Cleaning and Inspection
* Transfer Case Front Half Cleaning and Inspection Transfer Case Front Half Cleaning and Inspection
* Transfer Case Rear Half Cleaning and Inspection Transfer Case Rear Half Cleaning and Inspection

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