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Home >> Jeep >> 2021 >> Cherokee Trailhawk >> Repair and Diagnosis >> Engine Performance >> System >> 3.2L - DTCS P1239 To P2115 >> DTC Troubleshooting >> P1279-Starter Control Circuit 2 Open >> Diagnostic Test
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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 (ECUs) and record on the repair order.
    2. For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
    3. With the scan tool, erase all DTCs.
    4. Turn the ignition off for a minimum of 10.0 seconds.
    5. Turn the ignition on.
    6. Using the When Monitored and Set Conditions above and recorded data, 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. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.
      NOTE:

      If the vehicle has a no crank condition and/or DTC P141D is present along with this DTC, try replacing Starter Relay 2 and recheck for fault being active before proceeding.

      Is there a no crank condition and/or DTC P141D active or pending?

      Yes 

      • Replace the Starter Relay 2 and recheck for this DTC being active before proceeding.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  3
  3. CHECK THE ICR CONTROL RELAY AND PDC FOR PROPER OPERATION 
    1. Turn the ignition on.
    2. Using a 12-volt test light connected to ground, back probe the ICR Control Relay (T762) Control circuit at the PDC C2 connector.
    3. Using a 12-volt test light connected to ground, check that the test light is illuminated when probed to the ICR Control Relay (T760) Output circuit at the PDC C4 connector to verify the relay is closing when energized.
      NOTE:

      The relay may make an audible click when closing.

      Does the ICR Control Relay close when the control circuit is grounded?

      Yes 

      • Go To  4

      No 

      • Go To  6
  4. CHECK THE ICR CONTROL RELAY (T762) CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE 
    1. Measure the resistance of the ICR Control Relay (T762) Control circuit between the PDC C2 harness connector and the PCM C2 harness connector.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  5

      No 

      • Repair the ICR Control Relay (T762) Control circuit for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  5. CHECK RELATED PCM AND COMPONENT CONNECTIONS 
    1. Perform any Service Bulletins that apply.
    2. Disconnect all PCM harness connectors.
    3. Disconnect all related in-line harness connections (if equipped).
    4. Disconnect the related component harness connectors.
    5. 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.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
    9. With the scan tool, erase DTCs.
    10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    11. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      No 

      • The wiring or poor connection problem has been repaired.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  6. CHECK THE BATTERY SUPPLY VOLTAGE TO THE PDC 
    1. Using the wiring information as a guide, measure the main Battery supply voltage at the PDC terminal.

      Is Battery voltage present?

      Yes 

      • Check all fuses in the PDC. If a fuse is found to be open, replace the and retest. If no problems are found with the fuses, replace the Power Distribution Center (PDC) in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Repair the Battery voltage supply to the PDC for an open or high resistance.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
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