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Home >> Jeep >> 1996 >> Cherokee Classic, Part Time, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 4.0L >> Diagnostic Trouble Code (DTC) Identification >> Test TC-138A - Target Idle Not Reached

Test TC-138A - Target Idle Not Reached

NOTE: For connector terminal identification, refer to CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article in this section.
  1. Turn engine off, ignition on. With throttle linkage at idle position and throttle plate fully closed against its stop, check throttle plate and linkage for binding. Repair throttle plate and linkage as necessary and perform TEST VER-2A . If throttle linkage and plate are okay, go to next step.
  2. Start engine. Allow engine to idle for 60 seconds. If vehicle is equipped with automatic transmission, set parking brake, depress brake pedal and put gear selector in Drive. On all vehicles, use scan tool to read TARGET IDLE and engine speed (RPM). If engine RPM is within 200 RPM of target idle, go to step 5). If engine RPM is not within 200 RPM of target idle, go to next step.
    NOTE: The following test step is invalid if engine has any vacuum leaks.
  3. Check engine, brake booster and vacuum hoses for leaks. Ensure PCV valve is operating properly. Repair vacuum leaks or replace PCV valve as necessary and perform TEST VER-2A . If no vacuum leaks exist and PCV valve is operating properly, go to next step.
  4. Start engine. Allow engine to warm up. Using a scan tool, actuate the IAC wiggle test. Idle speed should raise and lower with scan tool display. If the IAC motor does not operate as specified, perform TEST TC-25A . If the IAC motor operates as specified, perform TEST TC-138B .
  5. Condition required to set DTC is not present at this time. TARGET IDLE NOT REACHED DTC sets if PCM senses target idle is not within 200 RPM of target idle for 2.96 milliseconds. Possible causes are: IAC driver circuit shorted to ground, IAC driver circuit shorted to battery, IAC driver circuits shorted together, defective PCM, IAC motor shorted internally, carbon deposits, open driver circuit, defective connector terminals or connector wires. Go to next step.
  6. Inspect all related wiring and connectors. Repair wiring and connectors as necessary and perform TEST VER-2A. If wiring and connectors are okay, go to next step.
  7. Wiggle harness from IAC motor to PCM. Observe for IAC motor to stop operating. If IAC motor stops operating, repair harness where wiggling caused motor to stop and perform TEST VER-2A. If IAC motor continues to operate, go to next step.
  8. Stop IAC motor wiggle test. See INACTIVE DTC CONDITION . Test is complete. Perform TEST VER-2A .
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