Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Test TC-16A - Idle Air Control Motor Circuits (DTC 25)
1994 Plymouth Voyager LE, 3.3 RSECTION Test TC-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.
- Turn ignition off. Connect a tachometer. Wait 10 seconds. Start engine. Allow engine to idle for 20 seconds. Using DRB, actuate Idle Air Control (IAC) motor to 1400 RPM. If tachometer does not read 1300-1500 RPM, go to step 5).
- If tachometer reads, 1300-1500 RPM, actuate IAC motor to 900 RPM using DRB. 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 trouble code is not present at this time. IDLE AIR CONTROL MOTOR CIRCUITS trouble code 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.
- 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. Ensure engine is warm. Using DRB, actuate IAC wiggle test. Idle speed should increase and decrease in relation to DRB display. If engine speed does not change as specified, go to step 5).
- 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 were found with wiring and connectors, see INACTIVE TROUBLE CODE CONDITION in this article. Perform TEST VER-2.
- Turn ignition off. Disconnect Idle Air Control (IAC) motor connector. Inspect IAC motor connector for damaged, pushed-out or misfired terminals. Repair as necessary. If connector is okay, go to next step.
- Using DRB in ohmmeter mode, check resistance of each wire on IAC motor connector. If resistance for any wire was less than 5 ohms, repair appropriate wire for a short to ground. Perform TEST VER-2.
- If resistance for all wires was more than 5 ohms, using DRB, actuate IAC motor. Using DRB in voltmeter mode, check voltage on each wire of IAC motor connector. If voltage for any wire was less than 5 volts at all times, go to appropriate test. See IAC DRIVER TEST table. If voltage for all wires was more than 5 volts at any time, go to next step.IAC DRIVER TEST
Driver No. Wire Color Test No. 1 BRN/WHT TEST TC-16B 2 YEL/BLK TEST TC-16C 3 GRY/RED TEST TC-16D 4 VIO/BLK TEST TC-16E - Turn ignition off. Using an external ohmmeter, check and record resistance between following driver circuits. See IAC DRIVER CIRCUIT IDENTIFICATION table:
- 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 was more than 5 ohms, replace IAC motor. Perform TEST VER-2.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.