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Home › Jeep › 2021 › Cherokee Trailhawk › Repair and Diagnosis › Engine Performance › System › 3.2L - DTCS P0073 To P0298 › DTC Troubleshooting › P0174-Fuel System 2/1 Lean › Diagnostic Test

Diagnostic Test

  1. CHECK THE ECT SENSOR FOR PROPER OPERATION 
    NOTE:

    For this test to be valid, the thermostat must be operating correctly.

    NOTE:

    This test works best if performed on a cold engine (cold soak).

    1. Ignition on, engine not running.
    2. With the scan tool, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a sensible value that is somewhere close to the ambient temperature.
      NOTE:

      If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.

    3. Start the Engine.
    4. During engine warm-up, monitor the Engine Coolant Temperature (ECT) Sensor value. The temperature value change should be a smooth transition from start up to normal operating temperature 82°C (180°F). The value should reach at least 82°C (180°F).

      Did the ECT value increase smoothly and did it reach at least 82°C (180°F)?

      Yes 

      • Go To  2

      No 

      • Verify that there is good pin to terminal contact in the ECT Sensor and Powertrain Control Module connectors. If OK, replace the Engine Coolant Temperature Sensor. Refer to 3.2L .
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  2. CHECK FOR AN ACTIVE DTC 
    NOTE:

    Check for contaminants that may have damaged an O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.

    1. Start the engine.
    2. Allow the engine to reach normal operating temperature.
    3. With the scan tool, read DTCs.
      NOTE:

      It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

      Is the DTC Active or Pending at this time?

      Yes 

      • Go To  3

      No 

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

      Are there any other DTCs active or pending?

      Yes 

      No 

      • Go To  4
  4. CHECK THE FUEL DELIVERY 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 

      • Repair as necessary in accordance with the service information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  5
  5. CHECK THE EXHAUST SYSTEM FOR LEAKS 
    1. Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure. Refer to CHECKING THE EXHAUST SYSTEM FOR LEAKS .

      Were any problems found?

      Yes 

      • Repair as necessary in accordance with the service information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  6
  6. CHECK THE O2 SENSOR 2/1 HEATER FOR PROPER OPERATION 
    1. Turn the ignition off.
      NOTE:

      Wait a minimum of 10 minutes to allow the O2 Sensor to cool down before continuing the test. Allow the O2 Sensor voltage to stabilize at 5.0 Volts.

    2. Ignition on, engine not running.
    3. With the scan tool, actuate the O2 Sensor 2/1 Heater Test.
    4. Using the scan tool, monitor O2 Sensor 2/1 voltage for at least two minutes.

      Does the voltage stay above 4.5 volts?

      Yes 

      • Verify that there is good pin to terminal contact in the O2 Sensor 2/1 and Powertrain Control Module connectors. Replace the O2 Sensor 2/1 if no problems were found with the connectors. Refer to 3.2L .
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  7
  7. CHECK THE MAP SENSOR FOR PROPER OPERATION 
    1. Perform the CHECKING THE MAP SENSOR OPERATION test procedure. Refer to CHECKING THE MAP SENSOR OPERATION .

      Were any problems found?

      Yes 

      • Repair as necessary in accordance with the service information.
      • Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .

      No 

      • Go To  8
  8. CHECK THE ENGINE FOR MECHANICAL PROBLEMS 
    1. Turn the ignition off.
    2. Check for any of the following conditions/mechanical problems:
      • AIR INDUCTION SYSTEM - must be free from leaks.
      • ENGINE VACUUM - must be at least 13 inches in neutral.
      • ENGINE VALVE TIMING - must be within specifications.
      • ENGINE COMPRESSION - must be within specifications.
      • ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks.
      • ENGINE PCV SYSTEM - must flow freely.
      • TORQUE CONVERTER STALL SPEED - must be within specifications.
      • POWER BRAKE BOOSTER - no internal vacuum leaks.
      • FUEL - must be free of contamination.
      • FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector.

      Are there any engine mechanical problems?

      Yes 

      No 

      • Go To  9
  9. CHECK THE 2/1 O2 SENSOR FOR PROPER OPERATION 
    1. Turn the ignition off.
    2. Replace the O2 Sensor and reconnect the harness connector.
    3. Turn the ignition on.
    4. With the scan tool, erase DTCs.
    5. Start the engine and allow it to idle long enough for the O2 Sensor to enter closed loop operation.
    6. With the scan tool, view DTCs.

      Did the DTC return?

      Yes 

      • Go To  10

      No 

  10. CHECK RELATED HARNESS CONNECTIONS 
    1. Disconnect all PCM 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.
      • Check for spread terminals and verify proper terminal tension.

      Repair any conditions that are found.

    5. Connect all PCM 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. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
    10. 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 .
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