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 FOR OTHER DTCS
1. Refer to the recorded DTCs.
  Are there any 5-Volt Reference DTCs present?
  
  Yes
  - Perform the applicable diagnostic procedure(s). Refer to DIAGNOSTIC CODE INDEX .
  No
  - Go To 3
CHECK THE FPS (K31) SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the FPS harness connector.
3. Turn the ignition on.
4. Measure the voltage on the FPS (K31) Signal circuit at the FPS harness connector.
  Is the reading above 5.2 volts?
  
  Yes
  - Repair the FPS (K31) Signal circuit for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE FPS (K31) SIGNAL CIRCUIT FOR A SHORT TO THE (N8) 5-VOLT SUPPLY CIRCUIT
1. Turn the ignition off.
2. Disconnected PCM C1 harness connector.
3. Disconnected PCM C2 harness connector.
4. Check for continuity between the FPS (K31) Signal circuit and the (N8) 5-Volt Supply circuit at the FPS harness connector.
  Is there continuity between the FPS (K31) Signal circuit and the (N8) 5-Volt Supply circuit?
  
  Yes
  - Repair the short between the FPS (K31) Signal circuit and the (N8) 5-Volt Supply circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE FPS (K31) SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Check for continuity of the FPS (K31) Signal circuit between the FPS harness connector and the PCM connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the FPS (K31) Signal circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (N10) SENSOR RETURN FOR AN OPEN/HIGH RESISTANCE
1. Check for continuity of the (N10) Return circuit between the FPS harness connector and the PCM connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 7
  No
  - Repair the (N10) Sensor Return circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE FUEL PRESSURE SENSOR
1. Turn the ignition off.
2. Reconnect the PCM C harness connectors.
3. Turn the ignition on.
4. While monitoring scan tool, connect a jumper between the FPS (K31) Signal circuit and the (N10) Sensor Return circuit at the FPS harness connector.
  NOTE:
  The PRESSURE SENSOR CIRCUIT LOW DTC should become active or pending with the jumper in place.
  
  Does the DTC display as described above?
  
  Yes
  - Replace the Fuel Pressure Sensor in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 8
POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Fuel Pressure Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Fuel Pressure Sensor and Control Module connectors.
4. Perform any Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace and program the Powertrain Control Module 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 .