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HOMESERVICE MANUALSJEEP2008LIBERTY SPORT, RWD, AUTOMATICREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMDTCS P0420 TO P0563P0507-IDLE SPEED PERFORMANCE HIGHER THAN EXPECTEDDIAGNOSTIC TEST
2008 Jeep Liberty Sport, RWD, Automatic

Diagnostic Test

2008 Jeep Liberty Sport, RWD, AutomaticSECTION Diagnostic Test
  1. ACTIVE DTC 
    NOTE: If any other Throttle Body DTCs are present, they must be diagnosed and repaired before continuing this test.

    Start the engine.

    WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

    Allow the engine to reach normal operating temperature.

    With a scan tool, select View DTCs.

    NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

    Is the DTC Active or Pending at this time? 

    Yes 

    1. Go To  2.

    No 

    1. Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
  2. AIR INDUCTION SYSTEM 

    Inspect the Air Induction System for the following problems:

    Leaks: Air Intake tube connection, Air Cleaner housing, etc.

    Were any problems found? 

    Yes 

    1. Repair or replace as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To  3.
  3. PCV SYSTEM 

    Inspect the PCV system for the following problems:

    Leaks - cracked or damaged hoses or tubes, poor hose or tube connections, PCV valve stuck open, etc.

    Were any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To  4.
  4. ENGINE VACUUM LEAKS 
    WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

    Start the engine.

    Inspect the vehicle for external vacuum leaks.

    Inspect the engine for internal leaks.

    Were any vacuum leaks found? 

    Yes 

    1. Repair the vacuum leak as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To  5.
  5. THROTTLE BODY OPERATION 

    Inspect the throttle body for carbon build up, other restrictions, and a bent throttle plate using a straight edge.

    WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

    While the vehicle is running, lightly tap on ETC Motor with your hand and listen for idle to raise.

    Were any problems found or did the idle fluctuate while tapping on the ETC Motor? 

    Yes 

    1. Verify that there is good pin to terminal contact at the Throttle Body and the Powertrain Control Module connectors. If OK, replace the Throttle Body Assembly. Disconnect the Battery when replacing the Throttle Body Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To  6.
  6. POWERTRAIN CONTROL MODULE (PCM) 

    Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Throttle Body and the Powertrain Control Module (PCM).

    Look for any chafed, pierced, pinched, or partially broken wires.

    Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Throttle Body and Powertrain Control Module connectors.

    Refer to any Technical Service Bulletins that may apply.

    Were there any problems found? 

    Yes 

    1. Repair as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace and program the Powertrain Control Module per Service Information.
    2. Perform POWERTRAIN VERIFICATION TEST .
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.