Jeep Liberty KJ. Manual — part 771
5.
MAF SENSOR
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Turn the ignition on.
Measure the voltage on the MAF Sensor 5-Volt Supply circuit at the
MAF Sensor harness connector.
Is the voltage below 5.5 volt?
Yes
>> Replace the MAF Sensor
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 6
6.
WIRING INSPECTION
Turn the ignition off.
Inspect the Boost Pressure Sensor 5-Volt supply circuit between the Boost Pressure Sensor harness connector and
the ECM harness connector for possible shorts to other circuits.
Inspect the Fuel Pressure Sensor 5-Volt supply circuit between the Fuel Pressure Sensor harness connector and
the ECM harness connector for possible shorts to other circuits.
Inspect the MAF Sensor 5-Volt supply circuit between the MAF Sensor harness connector and the ECM harness
connector for possible shorts to other circuits.
Were any problems found?
Yes
>> Repair shorted circuit as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
No
>> 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).
9 - 1142
ENGINE DIESEL DIAG
KJ
P0651-SENSOR SUPPLY 2 VOLTAGE TOO LOW
For a complete wiring diagram Refer to Section 8W
KJ
ENGINE DIESEL DIAG
9 - 1143
•
When Monitored:
With the ignition on.
•
Set Condition:
The ECM detects a low voltage for 0.1 second on the Sensor Supply #2 circuit which supplies 5-volts to the
MAF Sensor, Fuel Pressure Sensor and Boost Pressure Sensor.
Possible Causes
WIRING INSPECTION
INTERMITTENT CONDITION
5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
BOOST PRESSURE SENSOR
FUEL PRESSURE SENSOR
MAF SENSOR
ENGINE CONTROL MODULE
Diagnostic Test
1.
CHECK FOR ACTIVE 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.
Turn the ignition off for 10 seconds.
Turn the ignition on.
Monitor the scan tool for 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 - 1144
ENGINE DIESEL DIAG
KJ
2.
MASS AIR FLOW SENSOR SHORTED TO GROUND
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Turn the ignition on.
Measure the voltage of the MAF Sensor 5-Volt Supply circuit.
Is the voltage above 4.6 volts?
Yes
>> Replace the Mass Air Flow Sensor.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 3
3.
FUEL PRESSURE SENSOR SHORTED TO GROUND
Turn the ignition off.
Disconnect the Fuel Pressure Sensor harness connector.
Turn the ignition on.
Measure the voltage of the Fuel Pressure Sensor 5-Volt Supply circuit.
Is the voltage above 4.6 volts?
Yes
>> Replace the Fuel Pressure Sensor.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 4
KJ
ENGINE DIESEL DIAG
9 - 1145
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