Jeep Liberty KJ. Manual — part 684
•
When Monitored:
With the ignition on.
•
Set Condition:
The Fuel Rail Pressure Sensor signal voltage is above 4.8 volts.
Possible Causes
ECM - FUEL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
ECM - FUEL PRESSURE SENSOR SIGNAL OPEN
FUEL PRESSURE SENSOR SIGNAL CIRCUIT OPEN
FUEL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
SENSOR GROUND CIRCUIT OPEN
FUEL PRESSURE SENSOR 5-VOLT SUPPLY CIRCUIT OPEN
FUEL PRESSURE SENSOR GROUND CIRCUIT SHORTED TO VOLTAGE
FUEL PRESSURE SENSOR
ENGINE CONTROL MODULE
Diagnostic Test
1.
CHECKING FOR CURRENT DTC
WARNING: THE FUEL INJECTION PUMP SUPPLIES HIGH-PRESSURE FUEL TO EACH INDIVIDUAL INJEC-
TOR THROUGH HIGH-PRESSURE FUEL LINES. FUEL UNDER HIGH PRESSURE CAN PENETRATE SKIN AND
CAUSE PERSONAL INJURY. WEAR SAFETY GOGGLES AND ADEQUATE PROTECTIVE CLOTHING.
NOTE: If DTC P0641, P0651 or P0697 is present with this DTC, diagnose DTCs P0641, P0651 or P0697 before
diagnosing this DTC.
NOTE: If the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions
under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the
DTC is displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may
assist when checking for an active DTC.
Turn the ignition on.
With the scan tool, erase ECM DTCs.
Cycle the ignition key on and off several times, leaving the key on for at least 10 seconds at a time.
With the scan tool, read ECM DTCs.
Did this DTC set again?
Yes
>> Go To 2
No
>> Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
9 - 794
ENGINE DIESEL DIAG
KJ
2.
CHECK FUEL PRESSURE SENSOR SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Turn the ignition on.
Measure the voltage of the Fuel Pressure Sensor Signal circuit.
Select the appropriate voltage reading.
Voltage is above 5.5 volts.
Go To 3
Voltage is between 4.7 and 5.4 volts.
Go To 4
Voltage is below 4.7 volts.
Go To 9
3.
FUEL PRESSURE SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Disconnect the ECM harness connectors.
Remove the ASD Relay from the PDC.
Connect a jumper wire between cavity 30 and cavity 87 of the ASD
Relay connector.
Turn the ignition on.
Measure the voltage of the Fuel Pressure Sensor Signal circuit.
Is the voltage below 1.0 volt?
Yes
>> Replace and program the Engine Control Module in accor-
dance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Repair the Fuel Pressure Sensor Signal circuit for a short to
voltage.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
KJ
ENGINE DIESEL DIAG
9 - 795
4.
FUEL PRESSURE SENSOR GROUND CIRCUIT OPEN
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Fuel Pressure Sensor Ground circuit.
Is the resistance below 10.0 ohms?
Yes
>> Go To 5
No
>> Repair the Fuel Pressure Sensor Ground circuit for an
open.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
5.
FUEL PRESSURE SENSOR 5-VOLT SUPPLY CIRCUIT OPEN
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Fuel Pressure Sensor 5-Volt Supply cir-
cuit.
Is the resistance below 10.0 ohms?
Yes
>> Go To 6
No
>> Repair the Fuel Pressure Sensor 5-volt Supply circuit for an
open.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
9 - 796
ENGINE DIESEL DIAG
KJ
6.
FUEL PRESSURE SENSOR GROUND CKT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Disconnect the ECM harness connectors.
Remove the ASD Relay from the PDC.
Connect a jumper wire between cavity 30 and cavity 87 of the ASD
Relay connector.
Turn the ignition on.
Measure the voltage of the Fuel Pressure Sensor Ground circuit at the
Fuel Pressure Sensor and ECM harness connectors.
NOTE: If the Fuel Pressure Sensor Ground circuit had a short to
voltage on it, the ECM could be damaged. Retest the Fuel Pressure
Sensor circuit.
Is the voltage above 1.0 volt at either connector?
Yes
>> Repair the Fuel Pressure Sensor Ground circuit for a short
to voltage.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 7
7.
FUEL PRESSURE SENSOR
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Connect a jumper wire between the Fuel Pressure Sensor Signal circuit
and the Fuel Pressure Sensor Ground circuit in the Fuel Pressure Sen-
sor harness connector.
Turn the ignition on and monitor the scan tool for DTCs.
Is DTC P0190 FUEL PRESS SENSOR CIRCUIT MALF SIGNAL
VOLTAGE TOO LOW present?
Yes
>> Replace the Fuel Pressure Sensor.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 8
8.
ENGINE CONTROL MODULE
If there are no possible causes remaining, view repair.
Repair
Replace and program the Engine Control Module in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
KJ
ENGINE DIESEL DIAG
9 - 797
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