Test Description
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step checks that the scan tool is communicating with the transfer case shift control module (TCCM).
- 3: This step checks the presence of DTCs which begin with "U" indicating some other module is not communicating.
- 4: This step checks to see if other modules are interfering with the TCCM operation.
- 6: This step checks for TCCM DTCs.
- 7: This step verifies if the TCCM has power and ground. The TCCM will not communicate without the Battery Positive Voltage circuit functioning.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Install a scan tool. Does the scan tool power up? | Go to Step 2 | Go to Scan Tool Does Not Power Up in Data Link Communications |
| 2 | IMPORTANT: A new TCCM from the manufacturer comes with the latest calibrations for that vehicle. A Service/Replacement TCCM does not come with vehicle specific calibrations. If the scan tool does not communicate with the TCCM, it may be due to incomplete or missing files. Refer to Transfer Case Control Module Reprogramming . Turn ON the ignition, with the engine OFF. Attempt to establish communication with the TCCM. Does the scan tool communicate with the TCCM? | Go to Step 3 | Go to Step 7 |
| 3 | Does the scan tool display any current DTCs which begin with a "U"? | Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications | Go to Step 4 |
| 4 | Does the scan tool display any VSS DTCs? | Go to Diagnostic System Check - Automatic Transmission in Automatic Transmission - 4L80-E/4L85-E or Diagnostic System Check - Automatic Transmission in Automatic Transmission - Allison | Go to Step 5 |
| 5 | Does the scan tool display any Electronic Brake Control Module (EBCM) DTCs? | Go to Diagnostic System Check - ABS in Antilock Brake System | Go to Step 6 |
| 6 | Does the scan tool display any TCCM DTCs? | Go to Diagnostic Trouble Code (DTC) List | Go to Symptoms - Transfer Case |
| 7 | IMPORTANT: If there are multiple TCCM DTCs, diagnose the DTCs in the order listed in the DTC list. Test the battery positive voltage, ATC Class 2 Serial Data and ground circuits of the TCCM for an open, high resistance, short to ground and short to voltage.Did you find a condition with the circuits? | Go to Step 9 | Go to Step 10 |
| 8 | Flash the TCCM with the most current calibrations. Test drive the vehicle. Did the 4WD system operate normally without setting any DTCs? | System OK | Go to Step 3 |
| 9 | Repair the open, high resistance or short in the affected circuits. Did you complete the repair? | Go to Step 11 | |
| 10 | Replace the TCCM. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the replacement? | Go to Step 11 | |
| 11 | Test drive the vehicle. Does the vehicle 4WD system operate normally without setting any DTCs? | System OK | Go to Step 1 |
| IMPORTANT |
|---|
| A new TCCM from the manufacturer comes with the latest calibrations for that vehicle. A Service/Replacement TCCM does not come with vehicle specific calibrations. If the scan tool does not communicate with the TCCM, it may be due to incomplete or missing files. Refer to Transfer Case Control Module Reprogramming . |
| IMPORTANT |
|---|
| If there are multiple TCCM DTCs, diagnose the DTCs in the order listed in the DTC list. |
Diagnostic System Check - Transfer Case
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step inspects for the visual operation of the neutral Indicator. Command both the ON and OFF states.
- 3: This step tests for voltage at the neutral indicator feed side of the transfer case select switch.
- 4: This step verifies that the transfer case shift control module is providing ground to the neutral Indicator.
- 5: This step tests if ground is constantly being applied to the neutral indicator.
- 6: This step tests the control circuit of the neutral indicator for a short to voltage or an open.
- 7: This step tests the control circuit of the neutral indicator for a short to ground.
| 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 | Install a scan tool. Turn the ignition ON, with the engine OFF. With the scan tool, command the neutral control ON and OFF. Does the neutral turn ON and OFF with each command? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Turn the ignition OFF. Remove the transfer case select switch. Disconnect the connector on the transfer case select switch. Turn the ignition ON. Probe the ignition 3 voltage circuit with a DMM that is connected to a good ground. Does the DMM indicate battery voltage? | Go to Step 4 | Go to Step 10 |
| 4 | Connect a DMM between the harness connector of the neutral indicator control circuit and the ignition 3 voltage circuit. With the scan tool, command the neutral indicator ON and OFF. Does the DMM indicate battery voltage and then 0 volts with each command? | Go to Step 8 | Go to Step 5 |
| 5 | Does the DMM continue to indicate battery voltage with each command? | Go to Step 7 | Go to Step 6 |
| 6 | Test the neutral indicator control circuit for a short to voltage or an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
| 7 | Test the control circuit of the neutral indicator for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
| 8 | Disconnect the transfer case shift control module connectors C1 and C2. Inspect for poor connections at the transfer case shift control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
| 9 | Inspect for poor connections at the harness connector of the transfer case shift control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
| 10 | Repair the ignition 3 voltage circuit of the transfer case select switch for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | |
| 11 | Replace the transfer case select switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 13 | |
| 12 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 13 | |
| 13 | Use the scan tool in order to clear the DTCs. 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 |
DTC B0790
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests for proper operation of the transfer case mode select switch.
- 3: This step tests the mode switch for proper resistance values in all mode switch states.
- 4: This step tests the switch signal wire for a short to ground, short to voltage, or high resistance
| Step | Action | Values | 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 | Install a scan tool. Start the engine. Set the parking brake. Place the transmission into Neutral. With a scan tool, observe the mode switch selected in the tech 2 transfer case data list. Select each of the modes. Does the scan tool indicate that the modes are in the correct state while pressing the mode buttons? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
| 3 | With the switch disconnected, connect a DMM between the mode switch signal circuit and the 5 volt reference circuit at the switch. Measure the resistance through the mode switch while pressing and holding each of the mode buttons and comparing values. Does the DMM indicate all resistance values within the specified ranges? | Normal: 8,635-9,544 ohms 4 HI: 630-696 ohms 2 HI: 1,440-1,592 ohms Neutral: 974-1,035 ohms 4 LO: 2,228-2,462 ohms | Go to Step 4 | Go to Step 5 |
| 4 | Test the switch signal and 5 volt reference circuits for a short to voltage, short to ground or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 6 | |
| 5 | Replace the mode switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 7 | ||
| 6 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 7 | ||
| 7 | Use the scan tool in order to clear the DTCs. 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 | |
DTC B2725
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the battery positive and ground circuits for poor connections.
- 3: This step tests the encoder motor for an internal short to ground.
- 4: This step helps isolate motor malfunctions from the transfer case shift control module and wiring.
- 5: This step test for an open, high resistance, short to ground or short to voltage.
| Step | Action | Values | 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 | Check the battery positive and ground circuits for poor connections. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 3 | |
| 3 | IMPORTANT: Use test leads designed for this connector and make firm contact with the leads. Turn off the ignition. Disconnect the encoder motor. With a DMM at the encoder motor pigtail connector, test motor control A and motor control B for a short to ground within the encoder motor. Is motor control A or motor control B shorted to ground? | Go to Step 6 | Go to Step 4 | |
| 4 | IMPORTANT: Use test leads designed for this connector and make firm contact with the leads. Turn OFF the ignition. Disconnect the encoder motor connector. Zero the DMM with ohms selected by touching the two leads. Connect the DMM between motor control A terminal and motor control B terminal and test the resistance in the encoder motor. Is the motor/encoder within the specified values? | 0.3-35 ohms | Go to Step 5 | Go to Step 6 |
| 5 | Disconnect the transfer case shift control module connectors C1 and C2. Test the motor A and motor B control circuits for a short to ground, short to voltage, open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 | |
| 6 | Replace the encoder motor. Refer to Transfer Case Encoder Motor Replacement . Did you complete the repair? | Go to Step 8 | ||
| 7 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 8 | ||
| 8 | Use the scan tool in order to clear the DTCs. 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 | |
| IMPORTANT |
|---|
| Use test leads designed for this connector and make firm contact with the leads. |
| IMPORTANT |
|---|
| Use test leads designed for this connector and make firm contact with the leads. |
DTC C0306
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step checks for a voltage reading on the scan tool.
- 3: This step tests the encoder circuit for a current malfunction.
- 4: This step tests for an internal encoder malfunction which is present only in certain areas of the encoder sensor.
- 5: This step tests for proper reference voltage at the encoder.
- 6: This step tests the 5-volt reference circuit for proper voltage when the low reference circuit is used as a ground.
- 8: This step tests the 5-volt reference encoder circuit for a short to voltage, short to ground, an open or high resistance.
- 9: After determining if the reference voltage measured in Step 4 is correct, Step 6 reviews the reading originally measured in Step 3 to see if it is higher or lower than what is expected. This step helps determine whether the encoder signal circuit is being pulled high or low.
- 10: This step tests the encoder signal circuit and the encoder low reference circuit for a short to voltage.
- 11: This step helps determine a faulty encoder.
- 12: This step tests the encoder signal circuit and the encoder low reference circuit for an open or a short to ground.
| Step | Action | Values | 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 | Install a scan tool. Turn the ignition ON with the engine OFF. With a scan tool, observe the different voltage parameters. Are the voltage parameters displayed? | Go to Step 3 | Go to Step 5 | |
| 3 | Install a scan tool. Start the engine. Set the park brake. Place the transmission in NEUTRAL. With a scan tool, observe the Encoder Return Voltage parameter in the transfer case data list. Select each of the mode positions. 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 4 |
| 4 | Does the voltage reading stay within the specified values at any position? | 0.5-4.5 V | Go to Step 13 | Go to Step 5 |
| 5 | Turn the ignition OFF. Disconnect the encoder motor. Turn the ignition ON with the engine OFF. 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 6 | Go to Step 8 |
| 6 | Test the low reference circuit by jumping from the 5-volt reference circuit pin A to the low reference circuit pin C at the encoder pigtail on the module side of the harness. Does the voltage reading stay within the specified values? | 4.8-5.2 V | Go to Step 9 | Go to Step 7 |
| 7 | Test the 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 15 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | |
| 8 | Test the 5-volt reference circuit for a short to voltage, short to ground, an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 | |
| 9 | Was the voltage reading measured in Step 4 greater than 5.2 volts? | Go to Step 10 | Go to Step 11 | |
| 10 | Test the encoder signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 | |
| 11 | Install a scan tool. Turn the ignition ON with the engine OFF. Using a fused jumper, probe between the 5-volt reference encoder circuit and encoder signal circuit. 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 13 | Go to Step 12 |
| 12 | Test the encoder signal circuit and the encoder low reference circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 | |
| 13 | Replace the encoder sensor. Refer to Encoder Motor Sensor Replacement . Did you complete the repair? | Go to Step 15 | ||
| 14 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 15 | ||
| 15 | Use the scan tool in order to clear the DTCs. 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 | |
DTC C0327
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests for proper reference voltage to the transfer case shift control module on the 4WD LO circuit.
- 3: This step tests the 4WD LO circuit for a short to voltage.
- 4: This step tests the 4WD LO circuit for an open or high resistance.
- 5: This step repairs the 4WD LO circuit for a short to voltage.
| Step | Action | Values | 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 | Turn the ignition OFF. Disconnect the transfer case shift control module. Turn the ignition ON, with the engine OFF. Measure the voltage between the 4WD LO circuit harness and ground. Is the voltage reading within the specified values? | 10-13.5 V | Go to Step 3 | Go to Step 4 |
| 3 | Disconnect the PCM, ECM, and TCM, if equipped. Measure the voltage between the 4WD LO circuit harness and ground. Is the voltage reading at the specified value? | 0 V | Go to Step 7 | Go to Step 5 |
| 4 | Test the 4WD LO circuit for an open, high resistance, or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 | |
| 5 | Repair the 4WD LO circuit for short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | ||
| 6 | Replace the PCM for 6.0L or 8.1L or replace the ECM for 6.6L LLY. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L or Engine Control Module (ECM) Replacement in Engine Controls - 6.6L or Powertrain Control Module (PCM) Replacement in Engine Controls - 8.1L. Did you complete the repair? | Go to Step 8 | ||
| 7 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 8 | ||
| 8 | Use the scan tool in order to clear the DTCs. 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 | |
DTC C0359
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the front axle circuit for a current malfunction.
- 3: This step helps determine if the failure is the result of a short to voltage or ground.
- 4: This step helps determine if the front axle control circuit is shorted to ground.
- 5: This step tests the integrity of the front axle switch and the ignition 3 voltage circuits.
- 6: This step tests the front axle control circuit for short to ground.
- 7: This step tests the front axle control circuit for short to voltage or ground.
- 8: This step tests the front axle switch signal circuit for a short to voltage.
- 9: This step tests the front axle ignition 3 voltage circuit and the front axle switch circuit for an open or short to ground.
- 10: This step tests the front axle control circuit and the front axle ground circuit for an open or high resistance.
| 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 | Install a scan tool. Turn the ignition ON, with the engine OFF. Place the transfer case into 2WD mode and change to 4WD. With a scan tool, observe the Front Axle Switch parameter in the Transfer Case Data List. Does the Front Axle Switch parameter change from Unlocked to Locked? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Place the transfer case into 2WD mode. Does the scan tool parameter continue to display Locked? | Go to Step 4 | Go to Step 5 |
| 4 | Disconnect the front axle switch/actuator. Does the parameter display Unlocked? | Go to Step 6 | Go to Step 8 |
| 5 | Turn the ignition OFF. Disconnect the front axle switch/actuator. Turn the ignition ON, with the engine OFF. Connect a fused jumper across the ignition 3 voltage (CKT 241) and the axle switch signal circuits. With a scan tool, observe the Front Axle Switch parameter in the Transfer Case Data List. Does the Front Axle Switch parameter change from Unlocked to Locked? | Go to Step 11 | Go to Step 10 |
| 6 | Turn the ignition OFF and disconnect the TCCM connectors C1 and C2. Test the front axle actuator control circuit for short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 7 |
| 7 | With the transfer case shift control module connected, turn the ignition ON, with the engine OFF. Place the transfer case into 2WD. Use a DMM to probe the front axle control circuit and check the module for an internal short to ground or voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did the DMM indicate continuity to ground? | Go to Step 12 | Go to Step 9 |
| 8 | Turn the ignition OFF. Disconnect the transfer case shift control module. Test the front axle switch signal circuit at the front axle actuator connector for a short to voltage. refer to Testing for a Short to Voltage in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
| 9 | Connect the transfer case control module connectors C1 and C2. Test the front axle switch signal circuit for short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 12 | Go to Step 10 |
| 10 | Test the front axle ignition 3 circuit, the front axle switch circuit, and the front axle control actuator ground 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 13 | Go to Step 12 |
| 11 | Replace the front axle switch/actuator. Refer to Electric Motor Actuator Replacement in Front Drive Axle. Did you complete the repair? | Go to Step 13 | |
| 12 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 13 | |
| 13 | Use the scan tool in order to clear the DTCs. 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 |
DTC C0379
The number below refers to the step number on the diagnostic table
- 2: This step replaces the transfer case shift control module.
| 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 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | System OK | |
DTC C0550
Symptoms - Transfer Case
| IMPORTANT | Perform the Diagnostic System Check - Transfer Case before using the symptom tables, in order to verify that the following conditions are true: DTCs are not set. The control modules can communicate via the serial data link. |
- Review the system operation in order to familiarize yourself with the system functions. Refer to «Transfer Case Description and Operation»(ref-184162-S41109205402005082200000) .
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
- Inspect the automatic transfer case for the proper fluid level.
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the electrical function of the front axle actuator and helps determine mechanical and electrical malfunctions.
- 3: This step tests for proper power and ground at the front axle actuator.
- 4: This step tests the operation of the front axle control circuit.
- 5: This step helps determine if the transfer case shift control module is able to monitor the front axle switch.
- 6: This step tests the front axle switch circuit for an open or high resistance.
- 7: This step measures the voltage between the front axle feed circuit and ground.
- 8: This step tests the front axle control circuit for an open or high resistance.
- 9: This step inspects the front axle for a mechanical malfunction.
- 10: This step tests for open fuse in the front axle feed circuit.
| Step | Action | Values | 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 | Install a scan tool. Turn the ignition ON, with the engine OFF. With a scan tool, command the front axle Unlocked and Locked. Does the front axle turn ON and OFF with each command? | Go to Step 9 | Go to Step 3 | |
| 3 | Turn the ignition OFF. Disconnect the front axle actuator. Turn the ignition ON, with the engine OFF. Measure the voltage between the ignition 3 voltage circuit and the front axle ground circuit at the front axle actuator. Is the voltage reading within the specified value? | 11-13 V | Go to Step 4 | Go to Step 7 |
| 4 | Connect a test lamp between the ignition 3 voltage circuit and the front axle actuator control circuit at the front axle actuator. Observe the test lamp while using the scan tool in order to engage the front axle. Does the test lamp illuminate? | Go to Step 5 | Go to Step 8 | |
| 5 | Connect a fused jumper wire between the ignition 3 voltage circuit and the front axle actuator signal circuit. Use the scan tool in order to read the Front Axle Switch status. Does the scan tool display the Front Axle Switch status Locked? | Go to Step 13 | Go to Step 6 | |
| 6 | Test the front axle actuator signal 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 15 | Go to Step 14 | |
| 7 | Measure the voltage between the ignition 3 voltage circuit and ground. Is the voltage reading within the specified range? | 9-14 V | Go to Step 12 | Go to Step 10 |
| 8 | Test the front axle control 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 15 | Go to Step 14 | |
| 9 | Inspect the front axle for a mechanical malfunction. Did you find and correct the condition? | Go to Step 15 | Go to Step 13 | |
| 10 | Test for open fuse in the front axle feed circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 11 | |
| 11 | Repair an open in the front axle feed circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 12 | Repair an open in the front axle ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 15 | ||
| 13 | Replace the front axle switch/actuator. Refer to Electric Motor Actuator Replacement in Front Drive Axle. Did you complete the repair? | Go to Step 15 | ||
| 14 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 15 | ||
| 15 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK | |
Front Axle Will Not Engage
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the electrical function of the front axle actuator and helps determine mechanical and electrical malfunctions.
- 3: This step tests for proper voltage and ground at the front axle actuator.
- 4: This step tests the operation of the front axle actuator control circuit.
- 5: This step tests the electrical function of the front axle actuator control circuit.
- 6: This step tests for proper supply voltage to the front axle actuator.
- 7: This step tests for open fuse in the ignition 3 voltage circuit.
- 8: This step tests the front axle actuator control circuit for an open or high resistance.
- 9: This step tests the front axle actuator signal circuit for an open or high resistance.
- 10: This step helps determine if the front axle actuator has a mechanical malfunction.
- 11: This step tests the front axle switch circuit for a short to voltage.
- 12: This step inspects the front axle for a mechanical malfunction.
| Step | Action | Values | 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 | Turn the ignition ON, with the engine OFF. Ensure that the vehicle is in 2WD mode Install a scan tool. Using the scan tool, observe the Front Axle Switch status. Does the scan tool display the Front Axle Switch status as Locked? | Go to Step 10 | Go to Step 3 | |
| 3 | Turn the ignition OFF. Disconnect the front axle actuator. Turn the ignition ON, with the engine OFF. Measure the voltage between the ignition 3 voltage circuit and the front axle ground circuit at the front axle actuator. Is the voltage reading within the specified values? | 11-13 V | Go to Step 4 | Go to Step 6 |
| 4 | Connect a DMM between the ignition 3 voltage circuit and the front axle control circuit at the front axle actuator. Observe the DMM, while using the scan tool in order to engage the front axle. Does the test lamp illuminate? | Go to Step 5 | Go to Step 8 | |
| 5 | Connect a fused jumper wire between the ignition 3 circuit and the front axle switch circuit. Using the scan tool, observe the Front Axle Switch status. Does the scan tool display the Front Axle Switch status Locked? | Go to Step 15 | Go to Step 9 | |
| 6 | Measure the voltage between the ignition 3 voltage circuit and ground. Is the voltage reading within the specified values? | 11-13 V | Go to Step 13 | Go to Step 7 |
| 7 | Test for an open fuse in the front axle feed circuit. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 14 | |
| 8 | Test the front axle control 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 17 | Go to Step 16 | |
| 9 | Test the front axle actuator signal 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 17 | Go to Step 16 | |
| 10 | Disconnect the front axle actuator. Use the scan tool in order to read the Front Axle Switch status. Does the scan tool display the Front Axle Switch status Locked? | Go to Step 11 | Go to Step 12 | |
| 11 | Test the front axle actuator signal circuit for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 | |
| 12 | Inspect the front axle for a mechanical malfunction. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 | |
| 13 | Repair an open in the front axle actuator ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 17 | ||
| 14 | Repair an open in the ignition 3 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 17 | ||
| 15 | Replace the front axle switch/actuator. Refer to Electric Motor Actuator Replacement in Front Drive Axle. Did you complete the repair? | Go to Step 17 | ||
| 16 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 17 | ||
| 17 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK | |
Front Axle Will Not Disengage
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the functionality of the mode switch.
- 3: This step tests the modules ability to operate the transfer case modes.
| 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 | Install a scan tool. Start the engine. Place the transmission into NEUTRAL. Set the park brake. Observe Commanded Mode Indicator states on the scan tool while selecting each of the Mode positions. Does the state change with the selection of any of the mode positions? | Go to Step 5 | Go to Step 3 |
| 3 | Use a scan tool in order to command through the modes of the transfer case shift control switch. With a scan tool, command through all Commanded Mode Indicator states. Does the Mode Indicator state change? | Go to Step 4 | Go to Step 5 |
| 4 | Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 6 | |
| 5 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 6 | |
| 6 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Transfer Case Shift Control Switch Inoperative
The number below refers to the step number on the diagnostic table.
- 2: This step determines whether the failure is the result of a malfunctioning transfer case shift control module or the IPC.
| 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Using the scan tool, command the SERVICE 4WD lamp OFF. Does the SERVICE 4WD Lamp turn OFF? | Go to Step 3 | Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages, and Console. |
| 3 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 4 | |
| 4 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Service Indicator Always On
The number below refers to the step number on the diagnostic table.
- 2: This step determines whether the failure is the result of a faulty transfer case shift control module or the IPC.
| 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Using the scan tool, command the SERVICE 4WD Lamp ON. Does the SERVICE 4WD Lamp turn ON? | Go to Step 3 | Go to Diagnostic System Check - Instrument Cluster in Instrument Panel, Gages, and Console. |
| 3 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 4 | |
| 4 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Service Indicator Inoperative
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the transfer case electrical control of the lamp circuits.
- 3: This step helps determine if there is a short to ground in the suspect indicator control circuits.
| 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Using the scan tool, command all the indicator lamps OFF. Do all the lamps go OFF? | Go to Step 5 | Go to Step 3 |
| 3 | Drive the vehicle to determine the transfer case mode. Use this information to determine which indicator control circuits are at fault. Disconnect the transfer case shift control switch. Test the suspect indicator control circuits for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
| 4 | Replace the mode switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 6 | |
| 5 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 6 | |
| 6 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Transfer Case Shift Control Switch Indicator Always On - Two or More
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step helps to determine if the transfer case shift control module has the ability to command the encoder motor.
- 3: This step determines if motor control A and motor control B circuits being shorted together is causing a shift block.
- 4: This step determines if the motor control A and motor control B circuits are shorted together within the module.
- 5: This step determines if a binding shift lever detent shaft is causing a shift block.
- 6: This step has the transfer case removed and repaired.
- 7: This step determines if the PNP switch is sending the correct range signal.
- 8: This step replaces the transfer case shift control module.
| Step | Action | Value | 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Go to ATC Data List on the scan tool and observe motor A and B current. Using the mode switch in the instrument panel, select the different modes. Does the scan tool indicate an amperage draw from the motor? | Go to Step 3 | Go to Step 7 | |
| 3 | Turn the ignition OFF. Disconnect the transfer case shift control module and the encoder motor. With a DMM, check to see if motor control A and motor control B are shorted together. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 4 | |
| 4 | Connect the transfer case shift control module. With a DMM, check motor control A and motor Control B circuits for being shorted together. Refer to Circuit Testing in Wiring Systems. Does the DMM indicate a resistance less than the specified value? | 100 ohms | Go to Step 8 | Go to Step 5 |
| 5 | Remove the encoder motor and check to see if the shift lever detent shaft is binding. Refer to Transfer Case Encoder Motor Replacement . Is the shift lever detent shaft binding? | Go to Step 6 | Go to Step 9 | |
| 6 | Remove the transfer case and repair. Refer to Transfer Case Assembly Replacement . Did you complete the repair? | Go to Step 10 | ||
| 7 | Check the instrument panel to see if the correct transmission range is being displayed. Is the correct range being displayed? | Go to Step 8 | Go to Diagnostic System Check - Automatic Transmission in Automatic Transmission 4L60-E/4L65-E or Diagnostic System Check - Automatic Transmission 4L80-E/4L85-E | |
| 8 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 10 | ||
| 9 | Replace the encoder motor. Refer to Transfer Case Encoder Motor Replacement . Did you complete the repair? | Go to Step 10 | ||
| 10 | Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for allowing the symptom to occur. Does the symptom still occur? | Go to Step 2 | System OK | |
Transfer Case Shift Control Switch Indicator Flashes, then Returns to Previous Mode
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step determines the position of the front axle switch.
- 3: This step helps determine if the front axle will not engage.
- 4: This step helps determine if the front axle will not disengage.
| 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Using a scan tool, observe the Front Axle Switch status. Does the scan tool display the Front Axle Switch status as Locked? | Go to Step 4 | Go to Step 3 |
| 3 | Using a scan tool, observe the Encoder Gear Position status. Is the transfer case in 4WD HI or 4WD Low mode? | Go to Front Axle Will Not Engage | Go to Step 5 |
| 4 | Using a scan tool, observe the Encoder Gear Position status. Is the transfer case in 2WD mode? | Go to Front Axle Will Not Disengage | Go to Step 5 |
| 5 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 6 | |
| 6 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Transfer Case Shift Control Switch Indicators Flash Continuously 15 Seconds or More
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step tests the transfer case electrical control of the lamp circuits.
- 3: This step helps determine module failures.
- 4: This step tests the affected indicator control circuit for an open or high resistance.
- 5: This step tests the LED dimming supply circuit for an open or short to ground.
| 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 | Turn the ignition ON, with the engine OFF. Install a scan tool. Using the scan tool, command all the indicators ON. Do all the indicators illuminate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Access the back of the mode switch. Backprobe the indicator control circuit of the affected indicator to ground. Does the affected indicator go ON? | Go to Step 7 | Go to Step 4 |
| 4 | Test the affected indicator control circuit for an open or high resistance. Did you find and correct the condition? | Go to Step 8 | Go to Step 5 |
| 5 | Test the LED dimming supply circuit for an open or short to ground. Did you find and correct the condition? | Go to Step 8 | Go to Step 6 |
| 6 | Replace the transfer case shift control switch. Refer to Transfer Case Shift Control Switch Replacement . Did you complete the repair? | Go to Step 8 | |
| 7 | Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement and Transfer Case Control Module Reprogramming . Did you complete the repair? | Go to Step 8 | |
| 8 | Use the scan tool in order to clear the DTCs. Operate the vehicle in order to determine if the symptom has been corrected. Is the symptom still present? | Go to Step 2 | System OK |
Transfer Case Shift Control Switch Indicator Inoperative - One or More