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.

READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN
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 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK THE CONDITION OF THE ENGINE OIL AND LUBRICATION SYSTEM
NOTE:
The following items must be considered before determining the cause of this DTC. Failure to do so may lead to misdiagnosis. For the MDS to enable the 4 cylinder mode, the oil pressure has to be approximately 25 psi. For the MDS to remain enabled in the 4 cylinder mode the engine oil pressure can not drop below 23.2 psi. When checking the engine oil pressure use a mechanical gauge.
- ENGINE MECHANICAL TOLERANCES OUT OF SPECIFICATION
- ENGINE OIL PRESSURE OUT OF SPECIFICATION
- LOW ENGINE OIL
- DETERIORATED OR DIRTY OIL
- CORRECT VISCOSITY
- ENGINE OIL CONTAMINATED (i.e., coolant and/or fuel)
1. If any of the above conditions are found, repair as necessary.
  Were any of the above conditions present?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 3
ISOLATE AND CHECK THE EOP SENSOR (G60) 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 4
  No
  - Repair the circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
ISOLATE AND CHECK THE (F855) 5-VOLT SUPPLY 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 5
  No
  - Repair the circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
ISOLATE AND CHECK THE (K918) SENSOR 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 6
  No
  - Repair the circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE OIL PRESSURE
1. Turn the ignition off.
2. Check the engine oil pressure in accordance with the Service Information.
  Does the engine have the proper oil pressure?
  
  Yes
  - Go To 7
  No
  - Repair the mechanical fault causing the low oil pressure condition.
REPLACE THE EOP SENSOR AND RETEST FOR DTCS
1. Turn the ignition off.
2. Replace the EOP sensor in accordance with the Service Information. Refer to ENGINE OIL PRESSURE AND TEMPERATURE SENSOR .
3. Connect the EOP and PCM 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
  - Go To 8
  No
  - Replacing the faulty component repaired the fault.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK RELATED PCM AND COMPONENT CONNECTIONS
1. Perform any Service Bulletins that apply.
2. Disconnect all PCM harness connectors.
3. Disconnect all related in-line harness connections (if equipped).
4. Disconnect the related component harness connectors.
5. 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.
6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
9. With the scan tool, erase DTCs.
10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
11. 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 AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .