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Test FC-16A - Idle Air Control Motor Circuits (DTC 25)

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION . For appropriate wiring diagram, see WIRING DIAGRAMS  at end of article.
  1. Using DRB-II, erase fault messages. Turn ignition off. Start engine. Allow engine to reach normal operating temperature. Using DRB-II, read fault messages. If DRB-II displays IDLE AIR CONTROL MOTOR CIRCUITS, go to step 5).
  2. If DRB-II does not display IDLE AIR CONTROL MOTOR CIRCUITS, using DRB-II, set engine speed to 1800 RPM, then to 700 RPM. If engine speed responded accordingly, go to next step. If engine speed did not respond accordingly, go to step 5).
  3. Condition required to set fault is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS fault sets if any of 4 Idle Air Control (IAC) motor wires are shorted to ground or battery voltage. Possible causes are: open IAC motor wires, IAC motor internally shorted or IAC motor wires shorted together. Go to next step.
  4. Inspect all related wiring and connectors and repair as necessary. Perform VERIFICATION PROCEDURE VER-2. If no problems were found with wiring and connectors, see INACTIVE FAULT CONDITION. Perform VERIFICATION PROCEDURE VER-2.
  5. Turn ignition off. Disconnect Idle Air Control (IAC) motor connector. Disconnect Powertrain Control Module (PCM) connector. Using DRB-II, check resistance of each wire on IAC motor connector. If resistance for any wire was less than 5 ohms, repair necessary wire for a short to ground. Perform VERIFICATION PROCEDURE VER-2.
  6. If resistance for all wires was more than 5 ohms, turn ignition on. Put DRB-II in voltmeter mode. Using DRB-II, check voltage on each wire of IAC motor connector. If voltage for any wire was more than one volt, repair necessary wire for a short to voltage. Perform VERIFICATION PROCEDURE VER-2.
  7. If voltage for all wires was less than one volt, turn ignition off. Using an external ohmmeter, check resistance of each wire between IAC motor connector and PCM connector. See PCM TERMINAL IDENTIFICATION table. If resistance for any wire was more than 5 ohms, repair open on necessary wire. Perform VERIFICATION PROCEDURE VER-2. If resistance for all wires was less than 5 ohms, go to next step.
    PCM TERMINAL IDENTIFICATION

    Wire Color Terminal No.
    Gray/Red 39
    Brown/White 40
    Violet/Black 59
    Yellow/Black 60
  8. Using an external ohmmeter, check resistance between following wires at PCM connector. Record resistance readings.
    • PCM connector terminal No. 39 (Gray/Red wire) and terminal No. 60 (Yellow/Black wire)
    • PCM connector terminal No. 59 (Violet/Black wire) and terminal No. 60 (Yellow/Black wire)
    • PCM connector terminal No. 39 (Gray/Red wire) and terminal No. 59 (Violet/Black wire)
    • PCM connector terminal No. 40 (Brown/White wire) and terminal No. 60 (Yellow/Black wire)
  9. If resistance between any 2 wires was less than 5 ohms, repair those wires for shorting together. Perform VERIFICATION PROCEDUREVER-2. If resistance between all pairs of wires was more than 5 ohms, reconnect PCM connector.
  10. Turn ignition on. Using DRB-II, actuate IAC motor. Put DRB-II in voltmeter mode. Using DRB-II, check voltage on each IAC motor connector wire at IAC motor connector. Normal voltage reading will switch from less than one volt to more than 10 volts.
  11. If voltage is switching at each IAC motor connector wire, replace IAC motor. Perform VERIFICATION PROCEDURE VER-2. If voltage is not switching at each IAC motor connector wire, replace PCM. Perform VERIFICATION PROCEDURE VER-2.
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