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Diagnostic Test

WARNING: This page is about a different car, the 2024 Jeep Grand Wagoneer L and 2024 Jeep Grand Wagoneer. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK FOR ANY SERVICE BULLETINS OR PCM SOFTWARE UPDATES 
    1. Check for any applicable Service Bulletins or Flash updates related to the DTC.

      Are there any applicable Service Bulletins or Flash updates?

      Yes 

      No 

      • Go To  2
  2. READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN 
    NOTE:

    Verify there is fuel on the fuel tank before continuing with this test procedure.

    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  3

      No 

  3. CHECK FOR OTHER DTCS 
    1. Refer to the recorded DTCs.

      Are there any Fuel Quantity Solenoid or Fuel Pump DTCs present?

      Yes 

      No 

      • Go To  4
  4. CHECK THE HIGH PRESSURE FUEL SYSTEM FOR A SIGNS OF A LEAK 
    NOTE:

    Do not run the engine when inspecting the high pressure fuel system for leaks. The system pressure can be extremely high.

    1. Visually inspect for signs of fuel leaks at the high pressure fuel tube and Fuel Injectors.

      Are any leaks present?

      Yes 

      • If the leak appears to be at the high pressure fuel tube, verify that the tube is torqued correctly. If the torque is correct, replace the high pressure fuel tube in accordance with the Service Information. If the leak appears to be at a Fuel Injector, perform the appropriate repair in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK THE FUEL RAIL PRESSURE SENSOR READINGS 
    1. Start the engine and allow it to idle.
    2. With the scan tool, monitor the actual fuel rail pressure and target fuel rail pressure readings.

      Are both fuel pressure readings approximately the same?

      Yes 

      No 

      • Go To  6
  6. COMPARE THE FUEL RAIL PRESSURE SENSOR AND LOW FUEL PRESSURE READINGS 
    1. With the scan tool, monitor the fuel rail pressure and low fuel pressure readings.

      Is the fuel rail pressure reading approximately the same as the low pressure reading?

      Yes 

      • Go To  13

      No 

      • Go To  7
  7. CHECK THE LOW PRESSURE FUEL SYSTEM FOR PROPER OPERATION 
    1. Perform the CHECKING THE FUEL DELIVERY SYSTEM test procedure. Refer to CHECKING THE FUEL DELIVERY SYSTEM (HARD START) .

      Were any problems found?

      Yes 

      • Perform the appropriate repair(s) in accordance with the Service Information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  8
  8. CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR PROPER VOLTAGE AT THE FUEL RAIL PRESSURE SENSOR HARNESS CONNECTOR 
    1. Turn the ignition off.
    2. Disconnect the harness connector at the component of the circuit being tested. Note:  The ECU harness connector should still be connected during this test step.
    3. Turn the ignition on.
    4. Set the DVOM to measure DC voltage.
    5. Connect the negative lead of the DVOM to a known good ground.
    6. With the positive lead of the DVOM, measure the voltage of the circuit being tested at the component harness connector.
      NOTE:

      Normal operating voltage should be between 4.8 and 5.2 volts.

      Does the circuit have the proper voltage present?

      Yes 

      • Go To  9

      No 

      • Repair the circuit for an open/high resistance or short.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  9. ISOLATE AND CHECK THE FUEL RAIL PRESSURE SENSOR (K914) RETURN 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 Electronic Control Unit (ECU) and the component harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit.
    3. Before measuring the resistance of any circuit, first measure the resistance between the two leads of the DVOM. Note:  The meter leads can add resistance to the measurement value.
    4. Connect the leads of the DVOM to the circuit being tested.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  10

      No 

  10. ISOLATE AND CHECK THE FUEL RAIL PRESSURE SENSOR (K359) PRESSURE SIGNAL 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 Electronic Control Unit (ECU) and the component harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit.
    3. Before measuring the resistance of any circuit, first measure the resistance between the two leads of the DVOM. Note:  The meter leads can add resistance to the measurement value.
    4. Connect the leads of the DVOM to the circuit being tested.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  11

      No 

  11. ISOLATE AND CHECK THE FUEL RAIL PRESSURE SENSOR (K179) PRESSURE SIGNAL 2 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 Electronic Control Unit (ECU) and the component harness connector containing the circuit being tested. Note:  Use the wiring diagram as a guide to follow the path of the circuit.
    3. Before measuring the resistance of any circuit, first measure the resistance between the two leads of the DVOM. Note:  The meter leads can add resistance to the measurement value.
    4. Connect the leads of the DVOM to the circuit being tested.

      Is the resistance below 3.0 Ohms?

      Yes 

      • Go To  12

      No 

  12. REPLACE THE FUEL RAIL PRESSURE SENSOR AND RETEST FOR DTCS 
    1. Turn the ignition off.
    2. Replace the component in accordance with the Service Information. Refer to FUEL RAIL PRESSURE SENSOR (FRPS) .
    3. Connect the component and Electronic Control Unit (ECU) harness connectors.
    4. Turn the ignition on.
    5. With the scan tool, erase all DTCs.
    6. Turn the ignition off for a minimum of 10.0 seconds.
    7. Turn the ignition on.
    8. Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
    9. With the scan tool, read DTCs.

      Did the DTC return?

      Yes 

      • Replace the High Pressure Fuel Pump in accordance with the Service Information. Refer to HIGH PRESSURE FUEL PUMP .
        NOTE:

        Prior to replacing the High Pressure Fuel Pump, inspect the inlet port for obstructions or debris. Once removed, inspect the Fuel Pump Cam Lobes for wear.

      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

  13. CHECK THE FUEL QUANTITY SOLENOID CONNECTOR AND TERMINALS 
    1. Turn the ignition off.
    2. Check the FQS harness connector for proper connection at the High Pressure Fuel Pump Assembly.
    3. Verify that the connector is completely plugged in and properly locked prior to disconnecting.
    4. Disconnect the FQS harness connector and check for pushed out, damaged or spread terminals.

      Were any issues found with the connector or terminals?

      Yes 

      • Repair the damaged terminal or properly connect and lock the FQS harness connector and retest for DTCs.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  14
  14. ISOLATE AND LOAD TEST THE FUEL QUANTITY SOLENOID 1 (N17) HIGH SIDE CONTROL CIRCUIT TO CHECK FOR HIGH RESISTANCE 
    1. The ignition must be off when performing a load test on a circuit.
    2. Isolate the circuit by disconnecting the Electronic Control Unit (ECU) and every component harness connector containing the circuit being tested.
    3. Connect the positive lead of the load test tool to the positive side of the Battery (A). Note:  Refer to the diagram below.
    4. Using an approved back probe tool, connect the negative lead of the load test tool to the circuit being tested at the one of the component harness connectors (B).
    5. Using an approved back probe tool and a fused jumper wire, connect the circuit being tested to the negative side of the Battery or a known good ground at the other component harness connector (C and D).
    6. The bulb on the load test tool should be illuminated and bright if there is no resistance in the circuit.
      NOTE:

      Note: Why load test a circuit?  A load test is used to determine if a circuit is capable of carrying the amperage needed to perform properly. The 3156 bulb in the load tool illustrated, is a simple but effective method of testing circuit functionality. A 3156 Bulb has approximately 6.0 Ohms of resistance when the bulb is powered  and draws approximately 2.0 amps of current. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .

      NOTE:

      Note:  A 12-volt test light can be substituted for the load test tool, but only  if the test light draws enough current to effectively load test the circuit. Many high impedance test lights draw very little amperage (less than 0.1 amps) and are not reliable to load test a circuit. To perform a proper load test of a circuit, the tool being used should draw more than approximately 0.75 amps.

      NOTE:

      Note: Why perform a Voltage Drop Test?  To verify with certainty there is not any resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. To do so perform the following:

      • Connect the leads of a DVOM to the alligator clips on the load test tool while the load test tool is connected in series with the circuit.
      • Compare the voltage drop across the bulb to the voltage reading across the Battery terminals.
      • The voltage dropped across the bulb should be equal to the voltage reading across the Battery terminals if there is no resistance in the circuit being tested.

      Example:  2.0 Ohms of resistance in the circuit being tested will cause the voltage measurement across the bulb to be 25% less than when compared to Battery voltage. The reason for this is that the 2.0 Ohms in the circuit makes up 25% of the total circuit resistance of 8.0 Ohms. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .

      CAUTION:

      Do not load test any circuits with components still connected to the circuit.

      NOTE:

      Compare the brightness of the bulb in the load test tool to that of a direct connection to Battery.

      GC0174954Courtesy of CHRYSLER GROUP, LLC

      Is the load test bulb illuminated and bright?

      Yes 

      • Go To  15

      No 

  15. ISOLATE AND LOAD TEST THE FUEL QUANTITY SOLENOID 1 (N18) LOW SIDE CONTROL CIRCUIT TO CHECK FOR HIGH RESISTANCE 
    1. The ignition must be off when performing a load test on a circuit.
    2. Isolate the circuit by disconnecting the Electronic Control Unit (ECU) and every component harness connector containing the circuit being tested.
    3. Connect the positive lead of the load test tool to the positive side of the Battery (A). Note:  Refer to the diagram below.
    4. Using an approved back probe tool, connect the negative lead of the load test tool to the circuit being tested at the one of the component harness connectors (B).
    5. Using an approved back probe tool and a fused jumper wire, connect the circuit being tested to the negative side of the Battery or a known good ground at the other component harness connector (C and D).
    6. The bulb on the load test tool should be illuminated and bright if there is no resistance in the circuit.
      NOTE:

      Note: Why load test a circuit?  A load test is used to determine if a circuit is capable of carrying the amperage needed to perform properly. The 3156 bulb in the load tool illustrated, is a simple but effective method of testing circuit functionality. A 3156 Bulb has approximately 6.0 Ohms of resistance when the bulb is powered  and draws approximately 2.0 amps of current. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .

      NOTE:

      Note:  A 12-volt test light can be substituted for the load test tool, but only  if the test light draws enough current to effectively load test the circuit. Many high impedance test lights draw very little amperage (less than 0.1 amps) and are not reliable to load test a circuit. To perform a proper load test of a circuit, the tool being used should draw more than approximately 0.75 amps.

      NOTE:

      Note: Why perform a Voltage Drop Test?  To verify with certainty there is not any resistance in the circuit being tested, perform a simple voltage drop test across the 3156 bulb of the load test tool. To do so perform the following:

    7. Connect the leads of a DVOM to the alligator clips on the load test tool while the load test tool is connected in series with the circuit.
    8. Compare the voltage drop across the bulb to the voltage reading across the Battery terminals.
    9. The voltage dropped across the bulb should be equal to the voltage reading across the Battery terminals if there is no resistance in the circuit being tested.

      10. Example:  2.0 Ohms of resistance in the circuit being tested will cause the voltage measurement across the bulb to be 25% less than when compared to Battery voltage. The reason for this is that the 2.0 Ohms in the circuit makes up 25% of the total circuit resistance of 8.0 Ohms. Read the CIRCUIT LOAD TESTING PROCEDURE for information on building a simple load test tool and for additional load testing information and alternative methods of load testing or voltage drop testing a circuit. Refer to CIRCUIT LOAD TESTING PROCEDURES .

    CAUTION:

    Do not load test any circuits with components still connected to the circuit.

    NOTE:

    Compare the brightness of the bulb in the load test tool to that of a direct connection to Battery.

    GC0174954Courtesy of CHRYSLER GROUP, LLC

    Is the load test bulb illuminated and bright?

    Yes 

    • Replace the High Pressure Fuel Pump in accordance with the Service Information. Refer to ASSEMBLY, FUEL PUMP, REMOVAL AND INSTALLATION .
      NOTE:

      Prior to replacing the High Pressure Fuel Pump, inspect the inlet port for obstructions or debris. Once removed, inspect the Fuel Pump Cam Lobes for wear.

    • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

    No 

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