Jeep Liberty KJ. Manual — part 621
3.
ENGINE MECHANICAL PROBLEM
Check for any of the following conditions/mechanical problems.
AIR INDUCTION SYSTEM - must be free from leaks
ENGINE VACUUM - must be at least 13 inches in neutral
ENGINE VALVE TIMING - must be within specifications
ENGINE COMPRESSION - must be within specifications
ENGINE EXHAUST SYSTEM - must be free of any restrictions or leaks
ENGINE PCV SYSTEM - must flow freely
TORQUE CONVERTER STALL SPEED - must be within specifications
POWER BRAKE BOOSTER - no internal vacuum leaks
FUEL - must be free of contamination
FUEL INJECTOR - plugged or restricted injector; control wire not connected to correct injector
Are there any engine mechanical problems?
Yes
>> Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 4
4.
O2 SENSOR
Ignition on, engine not running.
Disconnect the 2/2 O2 Sensor harness connector.
With the scan tool, monitor the 2/2 O2 Sensor voltage.
The O2 Sensor voltage should read 5.0 volts on the scan tool with the
connector disconnected.
Using a jumper wire, jump the (K243) O2 Sensor 2/2 Signal circuit to
the (K904) O2 Downstream Return circuit in the O2 Sensor harness
connector.
NOTE: The voltage should drop from 5.0 volts to 2.5 volts with the
jumper wire in place.
Did the O2 Sensor volts change from 5.0 volts to 2.5 volts?
Yes
>> Replace the O2 Sensor
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 5
9 - 542
ENGINE ELECTRICAL DIAGNOSTICS
KJ
5.
(K243) O2 SENSOR 2/2 SIGNAL CIRCUIT
Remove the jump wire.
Ignition on, engine not running.
With the scan tool, monitor the O2 Sensor voltage.
Is the voltage above 4.8 volts?
Yes
>> Go To 6
No
>> Check the (K243) O2 Sensor 2/2 Signal circuit for a open or
short to voltage. Inspect the O2 Sensor connector and the
PCM harness connector. If OK, replace and program the
Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
6.
(K399) O2 SENSOR 2/2 HEATER CONTROL CIRCUIT SHORT TO GROUND
Turn the ignition off.
Measure the resistance between ground and the (K399) O2 Sensor 2/2
Heater Control circuit in the O2 Sensor harness connector.
Is the resistance below 5.0 ohms?
Yes
>> Repair the short to ground in the (K399) O2 Sensor 2/2
Heater Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Go To 7
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
KJ
ENGINE ELECTRICAL DIAGNOSTICS
9 - 543
7.
(K904) O2 DOWNSTREAM RETURN CIRCUIT
Measure the voltage on the (K904) O2 Downstream Return circuit in the
O2 Sensor harness connector.
Is the voltage at 2.5 volts?
Yes
>> Check the fuel system for contaminants.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No
>> Check the (K904) O2 Downstream Return circuit for a short
to ground, open, or short to voltage. Inspect the O2 Sensor
connector and the PCM harness connector. If OK, replace
and program the Powertrain Control Module per Service
Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
9 - 544
ENGINE ELECTRICAL DIAGNOSTICS
KJ
P2099-DOWNSTREAM FUEL TRIM SYSTEM 2 RICH
For a complete wiring diagram Refer to Section 8W.
KJ
ENGINE ELECTRICAL DIAGNOSTICS
9 - 545
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