Test TC-23A - Idle Air Control Motor Circuits (DTC 25)

WARNING: This page is about a different car, the 1995 Jeep Grand Cherokee. 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 in this article. For wiring diagram, see WIRING DIAGRAMS section at the end of this article.

Turn ignition on with engine off. 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 6).
If tachometer reads 1300-1500 RPM, use scan tool to actuate IAC motor to 900 RPM. If tachometer does not read 800-1000 RPM, go to step 6). If tachometer reads 800-1000 RPM, condition required to set trouble code is not present at this time. Go to next step.
NOTE: PCM cannot detect an open IAC driver circuit or a stuck IAC motor.
IDLE AIR CONTROL MOTOR CIRCUITS trouble code sets if any of 4 Idle Air Control (IAC) motor wires is shorted to ground or battery voltage for 2.75 seconds while IAC motor is active. Possible causes are: IAC driver circuit shorted to ground, IAC driver circuit shorted to voltage, IAC driver circuits shorted together, failed PCM or IAC motor internally shorted. Go to next step.
Inspect all related wiring and connectors. Repair as necessary. Perform TEST VER-2 . If no problems are found with wiring and connectors, start engine. Allow engine to run until normal operating temperature is reached. 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 6).
If the engine speed changes as specified, wiggle the wiring harness from the IAC motor to the Powertrain Control Module (PCM) while observing the IAC motor's operation. If the IAC motor stops operating at any time, repair the 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 miswired terminals. Repair as necessary. Perform TEST VER-2 . If connector is okay, go to next step.
Using scan tool, check resistance of all wires 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 .
NOTE: Voltage may switch or remain constant during step 8).

If resistance for all wires is more than 5 ohms, use scan tool to actuate IAC motor. Using scan tool in voltmeter mode, check voltage on each IAC motor connector wire. If voltage for any wire is less than 5 volts at any time, go to appropriate test. Refer to the 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	Go To:
1	Brown/White	TEST TC-23B
2	Violet/Black	TEST TC-23C
3	Yellow/Black	TEST TC-23D
4	Gray/Red	TEST TC-23E

Turn ignition off. Disconnect Powertrain Control Module (PCM) connector. Using an external ohmmeter, check and record resistance readings between following driver circuits. Refer to the IAC DRIVER CIRCUIT IDENTIFICATION table:

IAC driver circuit No. 1 and circuits No. 2, 3 and 4.
IAC driver circuit No. 2 and circuits No. 3 and 4.

IAC driver circuit No. 3 and circuit No. 4.

IAC DRIVER CIRCUIT IDENTIFICATION

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

If resistance between any 2 wires is less than 5 ohms, repair those 2 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 .