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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 SCAN TOOL COMMUNICATION 
    1. Verify the scan tool can communicate with another vehicle.

      Does the scan tool communicate with another vehicle?

      Yes 

      • Go To  2

      No 

      • Contact the scan tool support.
  2. CHECK THE SCAN TOOL CONNECTION 
    1. Verify all terminals in the DLC are locked into place and there is no damage to the connector or terminals.

      Are all terminals in the DLC locked into place and no damage found to the connector or terminals?

      Yes 

      • Go To  3

      No 

      • Repair the DLC and terminals as needed. Once the repair is complete, check the communication between the scan tool and this vehicle.
  3. CHECK THE DLC (B+) CIRCUIT FOR AN OPEN 
    1. Connect a battery charger to the vehicle in accordance with Service Information to maintain a full state of charge throughout testing on this vehicle.
    2. Connect the (special tool #CH7002, Break Out Box, J1962, 16-Way) to the DLC.
      NOTE:

      Do not connect the scan tool to the Break Out Box.

    3. With a 12-volt test light connected to ground, check the DLC Fused (B+) circuit at the Break Out Box.
      NOTE:

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

      Does the test light illuminate brightly?

      Yes 

      • Go To  4

      No 

      • Repair the DLC Fused (B+) circuit for an open or high resistance.
  4. CHECK THE DLC GROUND CIRCUITS FOR AN OPEN 
    1. With a 12-volt test light connected to 12 volts, check the DLC Ground circuits at the Breakout Box.
      NOTE:

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

      Does the test light illuminate brightly?

      Yes 

      • Go To  5

      No 

      • Repair the DLC Ground circuit for an open or high resistance.
  5. DETERMINE THE STATUS OF THE VEHICLE 
    NOTE:

    Make sure all programmed keys for this specific vehicle are present during the following test steps.

    1. Turn the headlights on.
    2. Attempt to start the engine.
      NOTE:

      This step is checking for communication from module to module that may still be possible, even though communication between the vehicle and the scan tool is not.

      Did the engine start or attempt to start by cranking?

      Yes 

      • Go To  6

      No 

      • Go To  7
  6. VERIFY CAN C BUS VOLTAGE AT THE DLC 
    1. Turn the engine off (if the engine started) and turn the ignition to the run position.
      NOTE:

      The vehicle has an operational CAN C bus because the engine was able to crank or start.

      NOTE:

      Do not connect the scan tool to the Break Out Box.

    2. Measure the voltage on the CAN C Bus (+) circuit at the Breakout Box and note the results. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
    3. Measure the voltage on the CAN C Bus (-) circuit at the Breakout Box and note the results. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Are the CAN C circuit voltages within the specified values?

      Yes 

      • Contact scan tool support.

      No 

      • Using the wiring diagrams as a guide, continue to diagnosis and test the CAN C Bus circuits and connections from the DLC to the Star Connector for an open or high resistance.
      • Check all related CAN C bus wiring from the DLC to the Star Connector for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension and repair as necessary.
  7. CHECK THE CAN C BUS VOLTAGES AT THE DATA LINK CONNECTOR 
    1. Connect the (special tool #CH7002, Break Out Box, J1962, 16-Way) to the DLC.
      NOTE:

      Do not connect the scan tool to the Break Out Box.

    2. Measure the voltage on the CAN C Bus (+) circuit at the Breakout Box and note the results. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
    3. Measure the voltage on the CAN C Bus (-) circuit at the Breakout Box and note the results. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Determine which best describes the results found:

      NORMAL - CAN C (+) and (-) voltages 

      • Go To  8

      ABNORMAL - CAN C (+) and (-) voltages 

      • Go To  12
  8. CHECK THE CAN C BUS VOLTAGES AT THE REAR/BODY STAR CONNECTOR 
    NOTE:

    Depending on the vehicle, either Front and Rear CAN C Star Connectors or IP and Body CAN C Star Connectors will be used.

    1. Disconnect the 3 wire harness connector at the Rear/Body CAN C Star Connector and check the CAN C bus (+) and (-) voltages between ground and each circuit at the harness connector. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Are the CAN C Bus voltages within the specified values?

      Yes 

      • Go To  9

      No 

      • Repair the CAN C bus circuit(s) between the Front/IP and Rear/Body CAN C Star Connectors for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  9. CHECK THE CAN C BUS VOLTAGES AT THE BODY CONTROL MODULE (BCM) 
    1. Connect the 3 wire harness connector to the Rear/Body CAN C Star Connector.
    2. Connect the scan tool to the (special tool #CH7002, Break Out Box, J1962, 16-Way).
    3. Disconnect the BCM connector containing the CAN C circuits.
    4. Check the CAN C bus (+) and (-) voltages between ground and each circuit at the BCM connector. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Are the CAN C Bus voltages within the specified values?

      Yes 

      • Go To  10

      No 

      • Repair the CAN C bus circuit(s) between the Rear/Body Star Connector and the BCM for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  10. CHECK ALL FUSED B(+) CIRCUITS TO THE BCM 
    1. Disconnect the scan tool from the Break Out Box.
    2. Turn the ignition off.
    3. Disconnect the BCM harness connectors.
    4. With a 12-volt test light connected to ground, check the Fused B(+) circuits at the BCM harness connector(s).
      NOTE:

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

      Does the test light illuminate brightly on all power circuit feeds to the BCM?

      Yes 

      • Go To  11

      No 

      • Repair the Fused B (+) circuit(s) for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  11. CHECK ALL GROUND CIRCUITS TO THE BCM 
    1. With a 12-volt test light connected to 12 volts, check all Ground circuits at the BCM connector(s).
      NOTE:

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

      Does the test light illuminate brightly on all ground circuits?

      Yes 

      • Go to  19

      No 

      • Repair the Ground circuit(s) for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  12. CHECK THE CAN C BUS VOLTAGES AT THE DLC 
    NOTE:

    Depending on the vehicle, either Front and Rear CAN C Star Connectors or IP and Body CAN C Star Connectors will be used.

    1. Disconnect the 3 wire harness connector at the Rear/Body CAN C Star Connector.
    2. Check the CAN C bus (+) and (-) voltages between ground and each circuit at the DLC. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Are the CAN C Bus voltages within the specified values?

      Yes 

      • Go To  13

      No 

      • Go To  15
  13. CHECK THE CAN C BUS CIRCUITS TO THE MODULE 
    1. Connect the 3 wire harness connector to the Rear/Body CAN C Star Connector.
    2. Disconnect one 2 wire connector from the Rear/Body CAN C Star Connector.
    3. Measure the voltage on the CAN C (+) circuit at the DLC breakout box. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
    4. Measure the voltage on the CAN C (-) circuit at the DLC breakout box. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
      NOTE:

      If the voltage for each CAN C circuit does not read within the specified CAN C circuit voltage range, connect the 2 wire connector back to the Rear/Body CAN C Star Connector and disconnect a different one. Then, repeat the voltage measurements. Repeat as necessary until the CAN C circuit voltages read within the specified CAN C circuit voltage range.

      Did the CAN C voltages read within the specified CAN C circuit voltage range when one of the 2 wire connectors were disconnected?

      Yes 

      • Go To  14

      No 

      • Replace the Rear/Body CAN C Star Connector in accordance with Service Information.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  14. CHECK THE MODULE 
    1. Connect the 2 wire connector that allowed the CAN C Bus voltages to return to the normal operating range.
    2. Disconnect the associated module while monitoring the CAN C bus voltages at the DLC. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Did the CAN C Bus voltages return to normal operating range?

      Yes 

      • Replace the associated module in accordance with the Service Information.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Repair the CAN C Bus circuits between the Rear/Body Star Connector and the associated module for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  15. CHECK THE CAN C BUS VOLTAGES 
    1. Disconnect the 3 wire connector at the Front/IP CAN C Star Connector and check the CAN C bus (+) and (-) voltages at the DLC with the Breakout Box. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Did the CAN C Bus voltages return to normal operating range?

      Yes 

      • Repair the CAN C bus circuits between the Front/IP and Rear/Body CAN C Star Connectors for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Go To  16
  16. CHECK THE CAN C BUS CIRCUITS TO THE MODULES 
    1. Connect the 3 wire connectors to the Rear/Body CAN C Star Connector.
    2. Connect the 3 wire connectors to the Front/IP CAN C Star Connector.
    3. Disconnect one 2 wire connector from the Front/IP CAN C Star Connector.
    4. Measure the voltage on the CAN C (+) circuit at the DLC breakout box. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
    5. Measure the voltage on the CAN C (-) circuit at the DLC breakout box. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.
      NOTE:

      If the voltage for each CAN C circuit does not read within the specified CAN C circuit voltage range, connect the 2 wire connector back to the Front/IP CAN C Star Connector and disconnect a different one. Then, repeat the voltage measurements. Repeat as necessary until the CAN C circuit voltages read within the specified CAN C circuit voltage range.

      Did the CAN C Bus voltages return to normal operating range?

      Yes 

      • Go To  17

      No 

      • Go To  18
  17. CHECK THE MODULE 
    1. Connect the 2 wire connector that allowed the CAN C Bus voltages to return to the normal operating range.
    2. Disconnect the associated module while monitoring the CAN C bus voltages at the DLC. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Did the CAN C Bus voltages return to the normal operating range?

      Yes 

      • Replace the associated module in accordance with the Service Information.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Repair the CAN C Bus circuits between the Front/IP CAN C Star Connector and the associated module for an open or high resistance.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  18. CHECK THE CAN C BUS CIRCUITS FOR AN OPEN OR SHORT 
    1. Check the CAN C bus (+) and (-) circuits for continuity to ground, short to voltage and opens from the DLC to the Front/IP CAN C Star Connector. Compare the results to the NORMAL CAN CIRCUIT VOLTAGE TABLE.

      Is the CAN C bus wiring open or shorted?

      Yes 

      • Repair the CAN C bus circuits between the DLC and the Front/IP Star Connectors for a short to ground, short to voltage or an open.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

      • Replace the Front/IP CAN C Star Connector in accordance with Service Information.
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  19. 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 

      • Replace the Body Control Module (BCM) in accordance with the Service Information. (Refer to REMOVAL, BCM ).
      • Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .

      No 

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