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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 33 (Engine Controls - Tests W/Codes - 3.8L) >> Self-Diagnostic Tests >> Test TC-16A - Idle Air Control Motor Circuits (DTC 25)

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

WARNING: This page is about a different car, the 1995 Plymouth Voyager, 1995 Plymouth Grand Voyager, 1995 Dodge Grand Caravan, 1995 Dodge Caravan, and 1995 Chrysler Town & Country. 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 DIAGRAMS  section at the end of this article.
  1. Turn ignition off. Connect a tachometer. Wait 10 seconds. Start engine. Allow engine to idle for 20 seconds. Using scan tool, actuate Idle Air Control (IAC) motor to 1400 RPM. If tachometer does not read 1300-1500 RPM, go to step 5).
  2. If tachometer reads 1300-1500 RPM, actuate IAC motor to 900 RPM using scan tool. If tachometer does not read 800-1000 RPM, go to step 5). If tachometer reads 800-1000 RPM, turn ignition off. Condition required to set DTC is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS DTC sets if any of 4 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.
  3. Inspect all related wiring and connectors, and repair as necessary. Perform TEST VER-2. If no problems are found with wiring and connectors, start engine. Ensure engine is warm. Using scan tool, actuate IAC wiggle test. Idle speed should increase and decrease in relation to scan tool display. If engine speed does not change as specified, go to step 5).
  4. If engine speed changes as specified, wiggle wiring harness from IAC motor to Powertrain Control Module (PCM) while observing IAC motor operation. If IAC motor stops operating at any time, repair wiring harness as necessary. Perform TEST VER-2. If no problems are found with wiring and connectors, see the INACTIVE DTC CONDITION  . Perform TEST VER-2.
  5. Turn ignition off. Disconnect Idle Air Control (IAC) motor connector. Inspect IAC motor connector for damaged, pushed-out or miswired terminals. Repair as necessary. If connector is okay, go to next step.
  6. Using scan tool in ohmmeter mode, check resistance of each wire on IAC motor connector. If resistance for any wire is less than 5 ohms, repair appropriate wire for a short to ground. Perform TEST VER-2.
  7. If resistance for all wires is more than 5 ohms, using scan tool, actuate IAC motor. Using scan tool in voltmeter mode, check voltage on each wire of IAC motor connector. If voltage for any wire is less than 5 volts at all times, go to appropriate test. See IAC DRIVER TEST table. If voltage for all wires is more than 5 volts at any time, go to next step.
    IAC DRIVER TEST

    Driver No. Wire Color Test No.
    1 BRN/WHT 16B 
    2 YEL/BLK 16C 
    3 GRY/RED 16D 
    4 VIO/BLK 16E 
  8. Turn ignition off. Using an external ohmmeter, check and record resistance between following driver circuits. See IAC DRIVER CIRCUIT IDENTIFICATION  table.
    • Driver circuit No. 1 and circuits No. 2, 3 and 4.
    • Driver circuit No. 2 and circuits No. 3 and 4.
    • Driver circuit No. 3 and circuit No. 4.
  9. If resistance between any 2 wires is less than 5 ohms, repair those wires for shorting together. Perform TEST VER-2. If resistance between all pairs of wires is more than 5 ohms, replace IAC motor. Perform TEST VER-2.
IAC DRIVER CIRCUIT IDENTIFICATION

Driver No. Wire Color
1 Brown/White
2 Yellow/Black
3 Gray/Red
4 Violet Black
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