Jeep Liberty KJ. Manual — part 671
•
When Monitored:
Engine speed is between 500 and 5000 rpm.
•
Set Condition:
The Mass Air Flow Sensor signal is above 800 kg/h for 0.5 seconds.
Possible Causes
ASD RELAY OUTPUT CIRCUIT OPEN
ECM - 5-VOLT SUPPLY CIRCUIT
MAF SENSOR GROUND OPEN
MASS AIRFLOW SENSOR
MAF SENSOR 5 VOLT SUPPLY CIRCUIT OPEN
MAF SENSOR SIGNAL CIRCUIT OPEN
MAF SENSOR 5 VOLT SUPPLY CIRCUIT SHORTED TO THE MAF SENSOR GROUND CIRCUIT
MAF SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
ECM SENSOR GROUND CIRCUIT OPEN
MAF SENSOR 5 VOLT SUPPLY CIRCUIT SHORTED TO GROUND
MAF SENSOR SIGNAL CIRCUIT SHORTED TO THE MAF SENSOR GROUND CIRCUIT
MAF SENSOR 5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
MAF SENSOR CIRCUIT SHORTED TO VOLTAGE
ECM - MAF SENSOR SIGNAL CIRCUIT
Diagnostic Test
1.
VERIFY ACTIVE DTC
NOTE: If DTC P0641, P0651 or P0697 is present with this DTC, diagnose DTCs P0641, P0651 or P0697 before
diagnosing this DTC.
NOTE: Inspect the turbocharger inlet tube between the MAF Sensor and the turbocharger for damage,
restriction or poor connection. Any of these conditions can cause a MAF Plausibility 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 the ECM DTCs.
Test drive the vehicle.
With the scan tool, read the ECM DTCs.
Does the scan tool display a Mass Air Flow Sensor DTC?
Yes
>> Go To 2
No
>> Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
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ENGINE DIESEL DIAG
KJ
2.
VERIFY SENSOR 5 VOLT SUPPLY
NOTE: A malfunctioning EGR system can cause this DTC to set.
Refer to symptom Checking the EGR System in the Driveability
category to check EGR system operation.
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 in MAF
Sensor harness connector.
Is the voltage between 4.8 and 5.2 volts?
Yes
>> Go To 3
No
>> Go To 11
3.
MAF SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
Turn the ignition off.
Disconnect the MAF 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 MAF Sensor Signal circuit.
Is the voltage above 1.0 volt?
Yes
>> Repair the MAF Sensor Signal circuit for a short to voltage.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 4
4.
MAF SENSOR SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the MAF Sensor Signal circuit.
Is the resistance below 10.0 ohms?
Yes
>> Go To 5
No
>> Repair the MAF Sensor Signal circuit for an open
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
KJ
ENGINE DIESEL DIAG
9 - 743
5.
MAF SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the MAF Sensor Signal
circuit.
Is the resistance below 1000 ohms?
Yes
>> Repair the MAF Sensor Signal circuit for a short to ground.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 6
6.
MAF SENSOR SIGNAL CIRCUIT SHORTED TO THE MAF SENSOR GROUND CIRCUIT
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the MAF Sensor Signal circuit and the
MAF Sensor Ground circuit at of the MAF Sensor harness connector.
Is the resistance below 1000 ohms?
Yes
>> Repair the MAF Sensor Signal for a short to MAF Sensor
Ground.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
No
>> Go To 7
7.
VERIFY MAF SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Connect a jumper wire between MAF Sensor Signal circuit and the 5-volt supply circuit at the MAF Sensor harness
connector.
Turn the ignition on.
With the scan tool, read the MAF VOLTS.
Does the scan tool display between 4.0 and 5.5 volts?
Yes
>> Go To 8
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).
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ENGINE DIESEL DIAG
KJ
8.
MAF SENSOR GROUND OPEN
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the MAF Sensor Ground circuit between the
MAF Sensor and the ECM.
Is the resistance below 10.0 ohms?
Yes
>> Go To 9
No
>> Repair the MAF Sensor Ground circuit for an open.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
9.
ECM - SENSOR GROUND OPEN
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Turn the ignition on.
Measure the voltage between the 5-volt Supply circuit and the MAF
Sensor Ground circuit at the MAF Sensor harness connector.
Is the voltage above 4.5 volts?
Yes
>> Go To 10
No
>> Replace and program the ECM in accordance with the Ser-
vice Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
10.
ASD RELAY OUTPUT CIRCUIT OPEN
Turn the ignition off.
Disconnect the MAF Sensor harness connector.
Turn the ignition on.
With the scan tool, actuate the ASD Relay.
Measure the voltage of the 12-volt Supply circuit at the MAF Sensor
harness connector.
Is the voltage above 10.0 volts?
Yes
>> Replace the MAF Sensor.
Perform ROAD TEST VERIFICATION - VER-2.
No
>> Repair the ASD Relay Output circuit for an open.
Perform the ECM Verification Test Ver. 1 (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
KJ
ENGINE DIESEL DIAG
9 - 745
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