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Test TC-25A - Idle Air Control Motor Circuits

NOTE: For connector terminal identification, refer to CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article in this section.
  1. Ensure ignition is off for at least 10 seconds. Start engine and allow it to idle for 20 seconds. Using scan tool, actuate Idle Air Control (IAC) motor to 1400 RPM. If engine speed is not 1300-1500 RPM, go to step 7). If engine speed is 1300-1500 RPM, go to next step.
  2. Using scan tool, actuate IAC motor to 900 RPM. If engine speed is not 800-1000 RPM, go to step 7). If engine speed is 800-1000 RPM, go to next step.
  3. Condition required to set DTC is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS DTC sets if Powertrain Control Module (PCM) senses a short to ground or battery voltage on any of 4 IAC motor driver circuits while IAC motor is operating. PCM cannot detect an open circuit or stuck IAC motor. Possible causes are: grounded or shorted IAC motor wiring, defective connections, defective IAC motor or PCM. Go to next step.
  4. Check for defective wiring/connections at IAC motor and PCM. Repair wiring/connectors as necessary and perform TEST VER-2A . If wiring and connectors are okay, go to next step.
  5. Start engine and allow it to reach normal operating temperature. Using scan tool, actuate IAC wiggle test. Engine speed should increase and decrease in accordance with scan tool display. If engine speed does not operate correctly, go to step 7). If engine speed operates correctly, go to next step.
  6. Wiggle wiring harness from IAC motor to PCM. If IAC motor stops operating while moving wiring harness, repair wiring as necessary and perform TEST VER-2A. If IAC motor does not stop operating, stop IAC wiggle test. See INACTIVE DTC CONDITION . Test is complete. Perform TEST VER-2A.
  7. Ensure ignition is off. Disconnect IAC motor connector. Inspect connector and terminals for damage. Repair connector and terminals as necessary and perform TEST VER-2A . If connector and terminals are okay, go to next step.
  8. Using scan tool in ohmmeter mode, check resistance of IAC motor connector, driver No. 1 circuit (Violet/Black wire). If resistance is less than 5 ohms, repair short to ground in driver No. 1 circuit and perform TEST VER-2A. If resistance is 5 ohms or more, go to next step.
  9. Check resistance of IAC motor connector, driver No. 2 circuit (Brown/White wire). If resistance is less than 5 ohms, repair short to ground in driver No. 2 circuit and perform TEST VER-2A . If resistance is 5 ohms or more, go to next step.
  10. Check resistance of IAC motor connector, driver No. 3 circuit (Yellow/Black wire). If resistance is less than 5 ohms, repair short to ground in driver No. 3 circuit and perform TEST VER-2A. If resistance is 5 ohms or more, go to next step.
  11. Check resistance of IAC motor connector, driver No. 4 circuit (Gray/Red wire). If resistance is less than 5 ohms, repair short to ground in driver No. 4 circuit and perform TEST VER-2A . If resistance is 5 ohms or more, go to next step.
    NOTE: Voltage may switch or remain constant in steps 12)-15).
  12. Using scan tool, actuate IAC motor. Using scan tool in voltmeter mode, check voltage on IAC motor connector, driver No. 1 circuit (Violet/Black wire). If voltage is not present at any time, perform TEST TC-25B . If voltage is present at any time, go to next step.
  13. Check voltage on IAC motor connector, driver No. 2 circuit (Brown/White wire). If voltage is not present at any time, perform TEST TC-25C . If voltage is present at any time, go to next step.
  14. Check voltage on IAC motor connector, driver No. 3 circuit (Yellow/Black wire). If voltage is not present at any time, perform TEST TC-25D . If voltage is present at any time, go to next step.
  15. Check voltage on IAC motor connector, driver No. 4 circuit (Gray/Red wire). If voltage is not present at any time, perform TEST TC-25E . If voltage is present at any time, go to next step.
  16. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Inspect connectors and terminals for damage. Repair connectors and terminals as necessary and perform TEST VER-2A . If connector and terminals are okay, go to next step.
    NOTE: Steps 17)-20) check for short circuits between IAC motor driver circuits.
  17. Using an external ohmmeter, check resistance between IAC motor connector, driver No. 1 circuit (Violet/Black wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A . If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  18. Check resistance between IAC motor connector, driver No. 2 circuit (Brown/White wire) and each remaining circuit on IAC motor connector. If resistance less than 5 ohms between any 2 circuits, repair driver circuits shorted together and perform TEST VER-2A. If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  19. Check resistance between IAC motor connector, driver No. 3 circuit (Yellow/Black wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits that are shorted together and perform TEST VER-2A. If resistance is 5 ohms or more on all IAC motor driver circuits, go to next step.
  20. Check resistance between IAC motor connector, driver No. 4 circuit (Gray/Red wire) and each remaining circuit on IAC motor connector. If resistance is less than 5 ohms between any 2 circuits, repair driver circuits shorted together and perform TEST VER-2A . If resistance 5 ohms or more, replace IAC motor and perform TEST VER-2A.
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