Originally Posted by mopar4ya
I am fighting with the IAC motor on my 93. I don't think it is moving at all. Can anyone tell me if this works of of voltage or all grounds?? My car has a intermenting check engine light with a code 25. I am starting to think I have a wire shorting to ground or a bad computor. How can I test each wire at the IAC ?????.
Well, sounds me like I'd be getting a new IAC. Just because of the code 25. I think if you just got a new one you would be just fine. Anyway, maybe this will help you some on testing the wires:
Idle Air Control (IAC) Motor
See Figures 1 and 2
Fig. 1: Wiring schematic for the IAC motor-1993-95 models
Fig. 2: Pin color code connections for the IAC motor harness-1993-95 models
For this test, the Diagnostic Readout Box (DRB III) or an equivalent diagnostic tool is necessary to actuate the IAC pintle.
Allow the engine to warm up to normal operating temperature, then idle at normal engine speed.
Before testing any electrical component, inspect the wiring and connectors for damage. Also wiggle the connectors to ensure a that they are firmly engaged.
Unplug the IAC connector.
Using a voltmeter, measure each of the four terminals of the connector (wiring harness side) to engine ground (one at a time). Refer to the accompanying wiring illustration. While probing each terminal to ground, momentarily open and close the throttle.
If any one, or more, of the terminal circuits registers below 1.0 volt, refer to Step 8.
If all of the terminal circuits registered above 1.0 volt, proceed to the next step.
Turn the engine OFF.
Detach the PCM connector and check to make certain that all of the terminals are clean and tightly installed in the connectors.
Using an ohmmeter, test the resistance of each of the four circuits from the oxygen sensor and ensure the sensor is working properly. The PCM uses a reference signal from the oxygen sensor to control the IAC motor position. If the oxygen sensor is not working correctly, it will give a false IAC position.
If the resistance of any of the circuits is below 10.0 ohms, replace the PCM. If any of the circuits register resistance above 10.0 ohms, repair the wire circuit with the high resistance.
Inspect the engine for any vacuum leaks.
If any leaks are found, repair them and retest the IAC from the beginning.
Otherwise, continue to the next step.
For the following of steps, the DRB III scan tool or equivalent is required.
Remove the IAC from the throttle body; leave the harness connected to it.
Plug the scan tool into the data link connector, and actuate the IAC.
If the IAC pintle extends and retracts, the IAC is OK and should be reinstalled.
If the IAC does not extend or retract, the IAC is defective and a new one should be installed.
See Figures 3 and 4
Fig. 3: Wiring schematic for the IAC motor-1996-97 models
Fig. 4: Pin color code connections for the IAC motor harness-1996-97 models
Turn the engine ON for 10 seconds.
Turn the engine OFF.
Turn the engine ON for 20 seconds.
Using the DRB III scan tool or equivalent, actuate the IAC motor.
With a voltmeter, probe the IAC motors 4 drivers. Refer to the accompanying wiring illustration.
If the voltage is over 5 volts, perform the following test:
With an ohmmeter, check the resistance of the circuits 1-4 of the IAC driver.
If the resistance on each driver is below 5.0 ohms on any of the drivers, the drivers circuits are shorted together and must be repaired.
If the resistance is above 5 ohms, replace the the IAC motor.