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.

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, read DTCs. Copy DTC and Freeze Frame information.
3. With the scan tool, erase DTCs.
  WARNING:
  When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.
4. Start the engine and operate the vehicle under conditions similar to which the DTC was set.
5. With the scan tool, view the Misfire Monitor to see which cylinders are effected.
  NOTE:
  It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.
6. With a scan tool, read DTCs.
  Is the DTC active?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK FOR OTHER DTCS
1. Refer to the recorded DTCs.
  Are there any other DTCs active or pending?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to 2.4L - DIAGNOSTIC CODE INDEX .
  No
  - Go To 3
PERFORM A VISUAL INSPECTION OF THE ENGINE COMPONENTS AND ACCESSORIES
1. Visually inspect the engine for any of the following conditions:
  NOTE:
  Each of the following conditions can cause a misfire during most operating conditions with the exception of the out of balance tires or warped brake rotors.
  - Worn serpentine belt. Refer to BELT, SERPENTINE, DIAGNOSIS AND TESTING .
  - Binding or misaligned engine driven accessories: Examples: A/C Compressor, P/S Pump, Water pump, etc.
  - Engine vacuum leak in the area of the affected cylinder.
  - Improper mounting of the CKP Sensor.
  - Extremely out of balance tires or warped brake rotors.
  Were any of the above conditions present?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 4
CHECK THE OXYGEN SENSORS FOR PROPER OPERATION
1. Perform the diagnostic procedure for CHECKING THE OXYGEN SENSOR OPERATION. Refer to DIAGNOSIS AND TESTING .
  Were any problems found?
  
  Yes
  - Repair as necessary in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 5
CHECK FOR A FUEL OR IGNITION SYSTEM PROBLEM
1. Start the engine and allow it to idle long enough for the O2 Sensor to warm up and go into closed loop operation. This may take a couple of minutes.
2. With the scan tool, observe the voltage reading of the Downstream O2 Sensor.
  NOTE:
  If the misfire is caused by a lack of fuel condition, the O2 Sensor voltage will tend to stay at the low end of the range (approximately 2.5 volts). If the misfire is caused by a lack of or poor quality spark condition, the O2 Sensor voltage will tend to stay at the high end of the voltage range (approximately 3.5 volts).
  
  Does the Downstream O2 Sensor voltage reading tend to be staying at the low end (2.5 volts) or high end (3.5 volts) of the voltage range?
  
  High end of the range (3.5 volts)
  - Go To 6
  Low end of the range (2.5 volts)
  - Go To 8
CHECK THE IGNITION SYSTEM FOR PROPER OPERATION
WARNING:
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

NOTE:
When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit. It may be necessary to erase the DTC or reset the misfire monitor before proceeding with this step in order for the PCM to fire the Ignition Coil.
1. Perform the CHECKING THE IGNITION COIL OPERATION test procedure on the Ignition Coil of the cylinder that is misfiring. For Multiple Cylinder Misfire, check each Ignition Coil individually. Refer to DIAGNOSIS AND TESTING .
  Were any problems found?
  
  Yes
  - Repair as necessary in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 7
    NOTE:
    Reconnect the Fuel Injector harness connector before continuing.
CHECK FOR A FAULTY SPARK PLUG
1. Turn the ignition off.
2. Exchange the Spark Plug with a known good cylinder that was not indicating a misfire.
3. Start the engine and monitor the misfire monitor screen.
  Did the misfire switch to the known good cylinder?
  
  Yes
  - Replace the Spark Plug in accordance with the Service Information. Refer to SPARK PLUG, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 12
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, 2.4L .
  No
  - Go To 9
CHECK THE FUEL INJECTOR CONTROL OPERATION
1. Turn the ignition off.
2. Disconnect the Fuel Injector harness connector of the misfiring cylinder. For Multiple Cylinder Misfire, check each Fuel Injector individually.
3. Turn the ignition on.
  NOTE:
  When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit. It may be necessary to erase the DTC or reset the misfire monitor before proceeding with this step in order for the PCM to fire the Fuel Injector.
4. Install an Injector Noid light.
5. With the scan tool, actuate the Fuel Injector.
  Does the Noid light blink/flicker during the actuation?
  
  Yes
  - Verify that there is good pin to terminal contact in the related Injector and the Powertrain Control Module connectors. Replace the Fuel Injector. Refer to INJECTOR(S), FUEL, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 10
CHECK THE INJECTOR CONTROL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Remove the Injector Noid light.
3. Disconnect the PCM C2 harness connector.
4. Check for continuity between ground and the Injector Control circuit at the Fuel Injector harness connector of the misfiring cylinder.
  Is there continuity between ground and the Injector Control circuit?
  
  Yes
  - Go To 11
  No
  - Repair the Injector Control circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK THE INJECTOR CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
CAUTION:
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
1. Connect the (special tool #10436, Adapter, GPEC Diagnostic).
2. Measure the resistance of the Injector Control circuit between the Fuel Injector harness connector of the misfiring cylinder and the GPEC Adaptor.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 12
  No
  - Repair the Injector Control circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
CHECK THE MAP SENSOR FOR PROPER OPERATION
1. Perform the diagnostic procedure for CHECKING THE MAP SENSOR OPERATION. 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, 2.4L .
  No
  - Go To 13
CHECK THE ENGINE MECHANICAL SYSTEM
1. Perform the diagnostic procedure for CHECKING THE ENGINE MECHANICAL SYSTEM. Refer to CHECKING THE ENGINE MECHANICAL SYSTEM .
  Were any problems found?
  
  Yes
  - Repair as necessary in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - Go To 14
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
  - Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL, 2.4L/3.2L .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L .