Jeep Liberty KJ. Manual — part 639
4.
ACTIVE DTCS IN THE BCM
With the scan tool, select ECU View and select BCM.
Withe the scan tool, read active DTCs.
Are any Communication DTCs active in the BCM relating to the ABS System?
Yes
>> Replace the ABS Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
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ENGINE ELECTRICAL DIAGNOSTICS
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*CHECKING THE FUEL DELIVERY SYSTEM
For a complete wiring diagram Refer to Section 8W.
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ENGINE ELECTRICAL DIAGNOSTICS
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Possible Causes
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
(N1) FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
FUEL PUMP RELAY
FUEL PUMP
Diagnostic Test
1.
FUEL PUMP OPERATION
Ignition on, engine not running.
With a scan tool, actuate the Fuel System test.
NOTE: It may be necessary to use a mechanics stethoscope in the next step.
Listen for fuel pump operation at the fuel tank.
Does the Fuel Pump operate?
Yes
>> Go To 2
No
>> Go To 5
CAUTION: Stop All Actuations.
2.
FUEL PRESSURE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow
these instructions can result in personal injury or death.
Install a fuel pressure gauge at the engine.
Ignition on, engine not running.
With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Choose a conclusion that best matches your fuel pressure reading.
Below Specification
Go To 3
Within Specification
Test Complete.
Above Specification
Replace the fuel filter/fuel pressure regulator.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
CAUTION: Stop All Actuations.
3.
RESTRICTED FUEL SUPPLY LINE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure must be released.
Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.
Install special tool #6539 (5/16
9
) or #6631(3/8
9
) fuel line adapter and the fuel pressure gauge between the fuel sup-
ply line and the fuel pump module.
Ignition on, engine not running.
With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
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ENGINE ELECTRICAL DIAGNOSTICS
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NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Is the fuel pressure within specification now?
Yes
>> Repair/replace fuel supply line as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 4
CAUTION: Stop All Actuations.
4.
CHECKING FUEL INLET STRAINER
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure must be released. Failure to follow
these instructions can result in personal injury or death.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
Is the Fuel Inlet Strainer plugged?
Yes
>> Replace the Fuel Pump Inlet Strainer.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Replace the Fuel Pump Module.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.
(N1) FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
Turn the ignition off.
Remove the Fuel Pump Relay from the PDC.
Disconnect the Fuel Pump Module harness connector.
Measure the resistance of the (N1) Fuel Pump Relay Output circuit from
the relay connector to the fuel pump module connector.
Is the resistance below 5.0 ohms?
Yes
>> Replace the Fuel Pump Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Repair the open in the (N1) Fuel Pump Relay Output circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
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