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Test TC-138A - Target Idle Not Reached

NOTE: For connector terminal ID, see CONNECTOR IDENTIFICATION  Directory. For wiring diagram, see appropriate WIRING DIAGRAMS - NON-TURBO article.
  1. Turn ignition on with engine off. Check throttle plate and linkage for binding. Ensure throttle linkage is at idle position. Repair either condition as required. Perform TEST VER-2A. If both conditions are okay, go to next step.
  2. Start engine. Allow engine to idle for one minute. Using scan tool, read target idle and engine 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: For remainder of this test to be valid, engine must not have any vacuum leaks.
  3. Verify PCV valve is correct application and operating properly. If PCV valve is correct and operating properly, go to next step. If PCV valve is not correct or operating properly, repair as necessary. Perform TEST VER-2A.
  4. Start engine. With engine warm, using scan tool, actuate Idle Air Control (IAC) wiggle test. Idle speed should raise and lower with scan tool display. If IAC motor is operating properly, go to TEST TC-138B. If IAC motor is not operating properly, go to TEST TC-25A.
  5. Condition to set trouble code is not present at this time. TARGET IDLE NOT REACHED DTC sets if engine speed is not within a specified amount of target idle for 2.96 milliseconds. Possible causes are:
    • Idle Air Control (IAC) driver circuit shorted to ground
    • IAC driver circuit shorted to battery
    • IAC driver circuits shorted together
    • Failed Powertrain Control Module (PCM)
    • Shorted IAC motor
    • Engine carbon deposits
    • Open IAC driver circuit.
  6. Inspect all related wiring and connectors and repair as necessary. If no problems were found with wiring and connectors, go to next step. If related wiring and connectors were repaired, perform TEST VER-2A.
  7. Start engine. With engine warm, using scan tool, actuate Idle Air Control (IAC) wiggle test. Idle speed should raise and lower with scan tool display. If IAC motor is operating properly, go to next step. If IAC motor is not operating properly, go to TEST TC-25A.
  8. Observe IAC motor operation. Wiggle wiring harness from IAC motor to PCM. If IAC motor stops operating at any time, repair wiring harness as necessary where wiggling caused problem to appear. Perform TEST VER-2A.
  9. Stop IAC wiggle test. See INACTIVE TROUBLE CODE CONDITION . Test is complete. Perform TEST VER-2A.
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