CE Code P0505 and Bad Idle

[ChicagoGSX]

I have a CE light code P0505 which is an idle control malfunction. I removed the throttle body and cleaned it. I tested the ISC and got 47 ohms for all the pins. I tested the TPS and got 0.9 ohms increasing to 5000 as I opened the throttle. I believe that means they are functioning correctly. What else could be the problem?

 

[98RedGs]

I got the same thing as of right now.

Did anyone ever awnser you?

 

[Doug99RS]

Part of the test for this code involves the use of a dealership specific scan tool to actuate the Idle Air Control motor. The test continues on to check additional sections of the IAC circuit with a simple multi-meter.

Information about the IAC system can now be found in the Tech Article forum.

Chances are good that the 4g63 engine works somewhat close to this but I'm not certain. Please use this information as generic testing information for the 4g63 and slightly more specific for the 420A.

The 2gnt IAC connector has four pins (A, B, C & D). All four are driver circuits for the stepper motor inside the IAC motor.

Crank and start the engine. With it still running, disconnect the IAC motor connector. With the multi-meter in voltmeter mode, attatch the negative lead to battery negative. Touch the positive side to each of the driver pin-outs. The meter should read over 5 volts. If it does not then go on to the next section which tests the wiring from the IAC motor to the computer. If the voltage is above 5 volts on each circuit then the motor is probably bad and not able to do anything with the voltage it's getting.

With the Engine off, unplug the IAC motor connector. With your multi-meter in Ohmmeter mode, check the resistance from each pin to battery negative (Pin A to ground, Pin B to ground, and so on). There should be no continuity. This means that one circuit is not shorted to ground. Next check for continuity between each of the driver circuits (Pin A to B, A to C, etc, then B to C, B to D, etc.) Again there should be no continuity. This will tell you if the wiring harness has shorted together.

If you find Continuity between two or more pin-outs in the connector, then you will need to check the harness for wires that have melted or fused together. If you find continuity between any single or multiple pin and battery negative, then you will need to find where the harness is chaffed of damaged causing the wires to be able to short to ground.

If you do not have over 5 volts at the IAC motor connector with the car running, you have continuity from the PCM to the IAC motor connector then it may be possible that the computer itself is not commanding the Idle Air Control motor to actuate. This may involve the replacement of the PCM/ECU.
Doug