P0507 (w/o Electronic Throttle Control)

CIRCUIT DESCRIPTION
The Idle Air Control (IAC) valve is located in the throttle body of both Sequential Multi-port Fuel Injection (SFI) and Multi-port Fuel Injection (MFI) systems. The IAC valve consists of a movable pintle, driven by a gear attached to an electric motor, which is called a stepper motor. The IAC valve motor is a 2 phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time the polarity of a winding is changed. This change in polarity can be seen when observing a test lamp connected between ground or B+ and an IAC valve circuit while the Powertrain Control Module (PCM) is attempting to change engine RPM. The test lamp will flash ON or OFF each time the polarity is changed.

The PCM does not use a physical sensor to determine IAC pintle position. The PCM uses a predicted number of counts, 1 count represents 1 change in polarity which equals 1 step of the stepper motor. The PCM counts the steps that have been commanded to determine IAC pintle position. The PCM uses the IAC valve to control engine idle speed by changing the pintle position in the idle air passage of the throttle body. This varies the air flow around the throttle plate when the throttle is closed.

To determine the desired position of the IAC pintle at idle or during deceleration, the PCM refers to the following inputs:
^ Engine RPM
^ Battery voltage
^ Air temperature
^ Engine Coolant Temperature (ECT)
^ Throttle Position (TP) sensor angle
^ Engine load
^ Vehicle speed

When the ignition key is turned OFF after an ignition cycle, the PCM will first seat the IAC pintle in the air bypass bore. Next, the PCM will retract the pintle a predetermined amount of counts. This retraction allows the proper amount of air to bypass the throttle plate in order for the engine to start-up. This procedure is known as an IAC Reset.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106-P0108, P0112, P0113, P0117, P01 18, P0121, P0122, P0123, P0125, P0128, P0171, P0172, P0174, P0175, P0200, P0300, P0401, P0404, P0405, P0440, P0442, P0443, P0446, P0449, P1111, P1112, P1114, P1115, P1121, P1122, P1380, P1381, P1404, or P1441 are not set.
^ The engine run time is greater than 60 seconds.
^ The ECT is greater than 60°C (140°F).
^ The IAT is greater than -10°C (+14°F).
^ The Throttle Position (TP) sensor is less than 0.7 percent.
^ The Barometric Pressure (BARO) is greater than 65 kPa.
^ The Vehicle Speed Sensor (VSS) is less than 1.6 km/h (1 mph).
^ The ignition volute between 9-18 volts.
^ The above conditions are present for 2 seconds.

CONDITIONS FOR SETTING THE DTC
The actual engine speed is 100 RPM greater than the desired engine speed.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
Inspect for the following conditions:
^ The correct PCV valve, properly installed and proper operation of the PCV valve
^ Proper operation and installation of all air intake components
^ Proper installation and operation of the Mass Air Flow (MAF) sensor, if equipped
^ Evidence of tampering or damage to the following components:
- The throttle stop screw
- The throttle plate
- The throttle shaft
- The throttle linkage
- The cruise control linkage, if equipped
^ A skewed high TP sensor
^ Excess deposits in the IAC passage or on the IAC pintle
^ Excess deposits in the throttle bore or on the throttle plate
^ Vacuum leaks
^ A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve-refer to Symptoms - Computers and Control Systems. Symptom Related Diagnostic Procedures

If intermittents exist, Refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-4:

Steps 5-9:

Steps 10-16:

The numbers below refer to the step numbers on the diagnostic table.
5. This test will determine the ability of the engine controller and IAC valve circuits to control the IAC valve.
7. This test will determine the ability of the PCM to provide the IAC valve circuits with a ground. On a normally operating system, the test lamp should not flash while the IAC counts are incrementing.