Question about 1999 Dodge Ram

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Computer code p0505 -running at high idle - 1999 Dodge Ram

Posted by rsouza130 on


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Jeffrey Turcotte

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Hi, not sure which engine you have so I can't be precise, but here is what I recommend. Remove the idle air control valve and check the valve seat for blockage. If dirty, clean both the passages and the valve, reinstall and see if that resolves the code. If it isn't blocked or dirty, run the tests below using a volt/ohmmeter. The primary test to run is step 8. If the valve fails step 8, replace the valve. If it passes, then check the PCM reference voltages in step 7. Let me know if you have questions.

computer code p0505 -running at - jturcotte_1104.gif

TESTING Conclusive testing of this component requires the use of special, factory-supplied equipment and is not included here. The tests below will provide valuable information regarding condition of the IAC motor and require only a VOM.

  1. Ignition must be OFF .
  2. Disconnect the IAC motor connector.
  3. Disconnect the PCM harness connector(s).
  4. Measure the resistance of the four IAC motor wires between the motor connector and the PCM connector. Refer to the illustrations for wire colors.
  5. Resistance should be under 5.0 ohms. Replace any wire with a higher resistance.
  6. Check for resistance between each motor lead and ground. Replace any wire with resistance under 5.0 ohms.
  7. Remove the ASD relay from the PDC (location is shown on the underside of the PDC cover. Connect a jumper between cavity 30 and 87 . Turn the ignition ON . Measure the voltage at each of the driver wires. Voltage should not exceed 1.0 v.
  8. With the ignition OFF and the IAC and PCM connectors detached, measure the resistance between each driver wire and ground. Resistance must be above 5.0 ohms in each case.

Fig. IAC motor assembly

Fig. IAC motor eleccomputer code p0505 -running at - jturcotte_1106.gifinouts


Fig. IAC motor and driver circuits

The IAC motor is located on the rear of the throttle body secured by two Torx® screws.

  1. Disconnect the negative battery cable.
  2. Remove the air cleaner assembly.
  3. Unplug the IAC motor connector.
  4. Remove the two mounting Torx® screws.
  5. Remove the IAC motor from the throttle body.

WARNING When the IAC motor is removed from the throttle body, do NOT extend the pintle more than 0.250 inch (6.35mm). If the pintle is extended more than this amount, it may separate from the IAC motor and the motor will have to be replaced.

To install:
  1. Install the IAC motor in the throttle body.
  2. Tighten the mounting bolts to 60 inch lbs. (7 Nm).
  3. Plug the IAC electrical connector in.
  4. Install the air cleaner assembly.Connect the negative battery cable.

Fig. IAC motor mounting screws (arrows)

Posted on Feb 26, 2011


Josh Marxen

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Idle control system malfunction.
The idle air control motor is on the back side of the throttle body. Make sure the connections are clean to it., but if you have to replace parts, I would start with the throttle position sensor on the side of the throttle body. It's cheaper and more likely the cause.

Posted on Feb 26, 2011



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If its running at a high idle I would test my Throttle position sensor and the idle air valve to make sure that there working properly.Next check and make sure that all you vacuum hoses are connected and not cracked or broken.You can find a diagram on the underside of the hood or on the radiator support near the fan shroud.

Posted on Feb 25, 2011

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Jeremy Moore

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SOURCE: 1999 Ram 3500 Wagon with

The IAC stepper motor is mounted to the throttle body, and regulates the amount of air bypassing the control of the throttle plate. As engine loads and ambient temperatures change, engine rpm changes. A pintle on the IAC stepper motor protrudes into a passage in the throttle body, controlling air flow through the passage. The IAC is controlled by the Powertrain Control Module (PCM) to maintain the target engine idle speed.

At idle, engine speed can be increased by retracting the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by restricting the passage with the pintle and diminishing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is moved (rotated) in steps, or increments. Opening the IAC opens an air passage around the throttle blade which increases RPM.

The PCM uses the IAC motor to control idle speed (along with timing) and to reach a desired MAP during decel (keep engine from stalling).

The IAC motor has 4 wires with 4 circuits. Two of the wires are for 12 volts and ground to supply electrical current to the motor windings to operate the stepper motor in one direction. The other 2 wires are also for 12 volts and ground to supply electrical current to operate the stepper motor in the opposite direction. To make the IAC go in the opposite direction, the PCM just reverses polarity on both windings. If only 1 wire is open, the IAC can only be moved 1 step (increment) in either direction. To keep the IAC motor in position when no movement is needed, the PCM will energize both windings at the same time. This locks the IAC motor in place.

In the IAC motor system, the PCM will count every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the memory is cleared, the PCM no longer knows the position of the pintle. So at the first key ON, the PCM drives the IAC motor closed, regardless of where it was before. This zeros the counter. From this point the PCM will back out the IAC motor and keep track of its position again.

When engine rpm is above idle speed, the IAC is used for the following:

  • Off-idle dashpot (throttle blade will close quickly but idle speed will not stop quickly)
  • Deceleration air flow control
  • A/C compressor load control (also opens the passage slightly before the compressor is engaged so that the engine rpm does not dip down when the compressor engages)
  • Power steering load control
The PCM can control polarity of the circuit to control direction of the stepper motor.

  1. First, try removing the IAC Valve, and cleaning the valve and the opening in the throttle body where the IAC Valve installs using Carburetor Cleaner. Ensure that the IAC Valve hole in the throttle body is not clogged, and is free from carbon deposits, etc. Have the ECM reset and check for the problem again.
  2. If the Check Engine Light comes back on, replace the IAC Valve. Have the ECM reset and check for the problem again.
  3. If the Check Engine Light still comes on, although highly unlikely, you may have a clogged throttle body, faulty wiring or connector, or faulty ECM (very unlikely since the vehicle runs).

I’m happy to help further over the phone at

Posted on Apr 13, 2011

tony chavous

tony chavous

  • 50 Answers

SOURCE: Engine code P0505 for 2002 honda odyssey

p0505 is directly related to the idle air control valve (sometimes called the rotary valve) i cant count how many of these i have replaced on hondas. It is located directly under the throttle body so it can be difficult to replace. I would recommend you having a professional replace this due to the difficulty of the valve removal

Posted on Feb 06, 2009

eleazar colin

  • 128 Answers

SOURCE: hello i have a 2001

well the ecu try to control the idle but if there is a leak on the intake maniful after the trotlebady it can not control it check for vamum leak may be a hose the pcv valve hose on the intake

Posted on Dec 15, 2010

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