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Diagnostic Test

  1. READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN 
    1. With the scan tool, read DTCs in all Electronic Control Units (ECU's) and record on the repair order.
    2. With the scan tool, run a Vehicle Scan Report, or record the Environmental Data.
    3. With the scan tool, erase DTCs.
    4. Turn the ignition off for at least 10.0 seconds.
    5. Turn the ignition on.
    6. Using the recorded Environmental Data and the When Monitored Conditions above, operate the vehicle in the conditions that set the DTC.
    7. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      • Go To  2

      No 

  2. ISOLATE AND CHECK THE (K77) TRANSFER CASE POSITION SENSOR INPUT CIRCUIT FOR A SHORT TO VOLTAGE 
    1. Turn the ignition off.
    2. Isolate the circuit by disconnecting the Electronic Control Unit (ECU) and every component harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit. Check the disconnected connectors and related harnesses for damage, corrosion, and loose fitting terminals.
    3. Turn the ignition on, engine not running.
    4. Measure voltage on the circuit being tested.

      Is there any voltage present?

      Yes 

      • Repair the circuit for a short to voltage.
      • Perform the DTCM VERIFICATION TEST. Refer to: DTCM VERIFICATION TEST .

      No 

      • Go To  3
  3. ISOLATE AND CHECK THE (K77) TRANSFER CASE POSITION SENSOR INPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. The ignition must be off when checking the continuity of a circuit.
    2. Isolate the circuit by disconnecting the ECU and the component harness connectors containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit. Check the disconnected connectors and related harnesses for damage, corrosion, and loose fitting terminals.
    3. Before testing a circuit, measure the resistance between the two leads of the Digital Volt-Ohm Meter (DVOM). Note:  Resistance in the meter leads can cause an error in the test results.
    4. Connect one lead of the DVOM to the circuit being tested at the component harness connector.
    5. Connect the other lead to the circuit being tested at the ECU harness connector and measure the resistance of the circuit.
      NOTE:

      When back-probing a circuit at a harness connector, always use an appropriate back probing tool to prevent damage to the connector terminals.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  4

      No 

      • Repair the circuit for an open or high resistance.
      • Perform the DTCM VERIFICATION TEST. Refer to: DTCM VERIFICATION TEST .
  4. REPLACE THE TRANSFER CASE SELECTOR SWITCH AND CHECK FOR THE DTC TO RETURN 
    1. Replace the Transfer Case Selector Switch in accordance with the Service Information.
    2. Connect the component and ECU harness connectors.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Using the Environmental Data or When Monitored information above, operate the vehicle under the conditions that set the DTC.
    6. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      • Go To  5

      No 

      • Replacing the Transfer Case Selector Switch corrected the condition.
      • Perform the DTCM VERIFICATION TEST. Refer to: DTCM VERIFICATION TEST .
  5. CHECK RELATED HARNESS CONNECTIONS 
    1. Disconnect all Drivetrain Control Module (DTCM) harness connectors.
    2. Disconnect all related in-line harness connections (if equipped).
    3. Disconnect the related component harness connectors.
    4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
      • Proper connector installation.
      • Damaged connector locks.
      • Corrosion.
      • Other signs of water intrusion.
      • Weather seal damage (if equipped).
      • Bent terminals.
      • Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
      • Terminals that have been pushed back into the connector cavity.
      • Perform a terminal drag test on each connector terminal to verify proper terminal tension.

      Repair any conditions that are found.

    5. Reconnect all DTCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    6. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    7. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. With the scan tool, erase DTCs.
    9. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    10. With the scan tool, read DTCM DTCs.

      Did the DTC return?

      Yes 

      No 

      • The wiring or poor connection problem has been repaired.
      • Perform the DTCM VERIFICATION TEST. Refer to: DTCM VERIFICATION TEST .
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