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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 24 (Engine Controls - Tests W/Codes - 2.5L) >> Self-Diagnostic Tests >> Test TC-12A - Idle Air Control Motor Circuits (DTC 25)

Test TC-12A - Idle Air Control Motor Circuits (DTC 25)

WARNING: This page is about a different car, the 1995 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: For circuit and connector terminal identification, see CONNECTOR IDENTIFICATION . For wiring diagrams, see WIRING DIAGRAM  section.
  1. Turn engine off. Turn ignition on. Start engine. Allow engine to idle for 20 seconds. Using scan tool, set engine speed to 1400 RPM. If engine speed is 1300-1500 RPM, go to next step. If engine speed is not 1300-1500 RPM, go to step 8).
  2. Using scan tool, reset engine speed to 900 RPM. If engine speed is 800-1000 RPM, go to next step. If engine speed is not 800-1000 RPM, go to step 8).
    NOTE: PCM cannot detect open IAC motor circuit or a stuck motor.
  3. Condition required to set DTC is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS DTC sets if any of the 4 Idle Air Control (IAC) motor wires are shorted to ground or shorted to battery voltage for 2.75 seconds while IAC motor is active. Go to next step.
  4. Inspect all related wiring and connectors and repair as necessary. Perform TEST VER-2. If no problems were found with wiring and connectors, start engine. Run engine until operating temperature is reached.
  5. Using scan tool, actuate IAC wiggle test. Idle speed should increase and decrease with scan tool display. If IAC motor operates properly, go to next step. If IAC motor does not operate properly, go to step 8).
  6. Wiggle Oxygen Sensor (O2S) connector and wiring harness while observing for IAC motor to stop functioning. If IAC motor does not stop functioning, go to next step. If IAC motor stops functioning, repair wiring harness as necessary. Perform TEST VER-2.
  7. Stop IAC wiggle test. If IAC wiggle test functions properly, see INACTIVE DTC CONDITION . Perform TEST VER-2.
  8. Turn ignition off. Disconnect Idle Air Control (IAC) motor connector. Inspect IAC motor connector for damaged or pushed-out terminals. Repair as necessary. Perform TEST VER-2. If IAC motor connector terminals are okay, put scan tool in ohmmeter mode.
  9. Using scan tool, check resistance of IAC connector Brown/White wire. If resistance is more than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short to ground in Brown/White wire. Perform TEST VER-2.
  10. Using scan tool, check resistance of IAC connector Yellow/Black wire. If resistance is more than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short to ground in Yellow/Black wire. Perform TEST VER-2.
  11. Using scan tool, check resistance of IAC connector Gray/Red wire. If resistance is more than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short to ground in Gray/Red wire. Perform TEST VER-2.
  12. Using scan tool, check resistance of IAC connector Violet/Black wire. If resistance is more than 5 ohms, go to next step. If resistance is less than 5 ohms, repair short to ground in Violet/Black wire. Perform TEST VER-2.
    NOTE: While measuring voltage in steps 13)-16), voltage may switch or remain constant.
  13. Using scan tool, actuate IAC motor. Put scan tool in voltmeter mode. Using scan tool, check voltage of IAC connector Brown/White wire. If voltage is more than 5 volts at any time, go to next step. If voltage is not more than 5 volts at any time, go to TEST TC-12B.
  14. Using scan tool, check voltage of IAC connector Yellow/Black wire. If voltage is more than 5 volts at any time, go to next step. If voltage is not more than 5 volts at any time, go to TEST TC-12C.
  15. Using scan tool, check voltage of IAC connector Gray/Red wire. If voltage is more than 5 volts at any time, go to next step. If voltage is not more than 5 volts at any time, go to TEST TC-12D.
  16. Using scan tool, check voltage of IAC connector Violet/Black wire. If voltage is more than 5 volts at any time, go to next step. If voltage is not more than 5 volts at any time, go to TEST TC-12E.
  17. Turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Inspect PCM connector for damaged or pushed-out terminals. Repair as necessary. Perform TEST VER-2. If PCM connector terminals are okay, go to next step.
  18. Disconnect Powertrain Control Module (PCM) connector. Using an external ohmmeter, check and record resistance between following wires at IAC motor connector.
    • Brown/White Wire And Yellow/Black Wire
    • Brown/White Wire And Gray/Red Wire
    • Brown/White Wire And Violet/Black Wire
  19. If resistance between any 2 wires is less than 5 ohms, repair those wires for shorting together. Perform TEST VER-2. If resistance between each pair of wires is more than 5 ohms, go to next step.
  20. Using an external ohmmeter, check and record resistance between following wires at IAC motor connector.
    • Yellow/Black Wire And Gray/Red Wire
    • Yellow/Black Wire And Violet/Black Wire
  21. If resistance between any 2 wires is less than 5 ohms, repair those wires for shorting together. Perform TEST VER-2. If resistance between each pair of wires is more than 5 ohms, go to next step.
  22. Using an external ohmmeter, check and record resistance between following wires at IAC motor connector.
    • Gray/Red Wire And Violet/Black Wire
  23. If resistance between wires is less than 5 ohms, repair wires for shorting together. Perform TEST VER-2. If resistance between wires is more than 5 ohms, replace IAC motor. Perform TEST VER-2.
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