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Diagnostic Test

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK FOR AN ACTIVE DTC 
    1. With the scan tool, read Body Control Module (BCM) DTCs and record on the repair order.
    2. Record the Environmental Data and any DTCs.
    3. With the scan tool, erase DTCs.
    4. Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
    5. With the scan tool, read BCM DTCs.

      Did the DTC return?

      Yes 

      • Go To  2

      No 

      • Test complete. The condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals and correct pin tension.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  2. CHECK THE FUEL HEATER RELAY FOR PROPER OPERATION 
    1. Turn the ignition off.
    2. Remove the Fuel Heater Relay from the Power Distribution Center (PDC) Assembly.
      NOTE:

      If the substituted relay does not change the DTC status to Stored, reinstall the relay that was previously removed.

    3. Temporarily substitute the relay with a known good relay.
    4. Turn the ignition on.
    5. With the scan tool, read DTCs.

      Does the scan tool display this DTC as active?

      Yes 

      • Go To  3

      No 

  3. CHECK THE CHECK THE BCM FUEL HEATER RELAY OUTPUT 
    1. Turn the ignition off.
    2. Remove the Fuel Heater Relay from the PDC Assembly.
    3. Turn the ignition on.
      NOTE:

      The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

    4. Using a 12-volt test light, connected to 12-volts, check the (K57) Fuel Heater Relay Control circuit at the Fuel Heater Relay terminal in the PDC Assembly.

      Does the test light illuminate brightly?

      Yes 

      • Go To  4

      No 

      • Go To  6
  4. CHECK THE (K57) FUEL HEATER RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND 
    1. Turn the ignition off.
    2. Disconnect the BCM C8 harness connector.
    3. Check for continuity between ground and the (K57) Fuel Heater Relay Control circuit at the BCM C8 harness connector.

      Is there continuity between ground and the (K57) Fuel Heater Relay Control circuit?

      Yes 

      • Go To  5

      No 

      • Go To  9
  5. CHECK THE PDC ASSEMBLY FOR AN INTERNAL SHORT 
    1. Disconnect the PDC Assembly C3 harness connector.
    2. Check for continuity between ground and the (K57) Fuel Heater Relay Control circuit at the BCM C8 harness connector.

      Is there continuity between ground and the (K57) Fuel Heater Relay Control circuit?

      Yes 

      • Repair the short to ground in the (K57) Fuel Heater Relay Control circuit.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Go To  8
  6. CHECK THE (K57) FUEL HEATER RELAY CONTROL CIRCUIT FOR AN OPEN 
    1. Turn the ignition off.
    2. Disconnect the BCM C8 harness connector.
    3. Measure the resistance of the (K57) Fuel Heater Relay Control circuit between the BCM C8 harness connector and the Fuel Heater Relay terminal in the PDC Assembly.

      Is the resistance above 3.0 Ohms?

      Yes 

      • Go To  7

      No 

      • Go To  9
  7. CHECK THE PDC ASSEMBLY FOR AN INTERNAL OPEN 
    1. Disconnect the PDC Assembly C3 harness connector.
    2. Measure the resistance of the (K57) Fuel Heater Relay Control circuit between the BCM C8 harness connector and the PDC Assembly C3 harness connector.

      Is the resistance above 3.0 Ohms?

      Yes 

      • Repair the open in the (K57) Fuel Heater Relay Control circuit.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Go To  8
  8. CHECK RELATED PDC ASSEMBLY HARNESS CONNECTIONS 
    1. Disconnect all PDC Assembly 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. Connect all PDC Assembly harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
    6. Connect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
    7. Connect 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 BCM DTCs.

      Did the DTC return?

      Yes 

      No 

  9. CHECK RELATED HARNESS CONNECTIONS 
    1. Disconnect all BCM 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 BCM 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 BCM DTCs.

      Did the DTC return?

      Yes 

      No 

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