P0506

Circuit Description
The powertrain control module (PCM) controls the engine idle speed by adjusting the position Of the idle air control (IAC) motor pintle. The IAC is a bi-directional motor driven by 2 coils. The PCM sends pulses (steps) to the IAC in order to extend or retract the IAC pintle into a passage in the Throttle body to decrease or increase air flow. The commanded IAC position (displayed in counts) may be monitored on a scan tool. A higher number Of counts indicates more commanded airflow (pintle retracted). This method allows highly accurate control of idle speed and quick response to changes in the engine load. If the PCM detects a condition where a too low idle speed is present and the PCM is unable to adjust idle speed by increasing the IAC counts, DTC P0506 is set indicating a problem with the idle control system.

Conditions for Running the DTC
^ None of the following DTCs are set:
- Throttle position (TP) sensor DTCs
- Vehicle speed sensor (VSS) DTCs
- Evaporative emissions (EVAP) system DTCs
- Intake air temperature (IAT) sensor DTCs
- Manifold absolute pressure (MAP) sensor DTCs
- Exhaust gas recirculation (EGR) pintle position DTCs
- Engine coolant temperature (ECT) sensor DTCs
- Crankshaft position (CKP) sensor DTCs
- Mass air flow (MAF) sensor DTCs
- Misfire DTCs
- Fuel trim DTCs
- Fuel injector DTCs

^ The BARO is greater than 65 kPa.
^ The engine is running for at least 60 seconds.
^ The system voltage is between 9 arid 16 volts.
^ The ECT is more than 70°C (158°F).
^ The vehicle speed is less than 3 MPH.
^ The IAT is more than -18°C (0°F).
^ The Throttle is closed.

Conditions for Setting the DTC
^ The engine speed is over 100 RPM lower than the Desired Idle.
^ The above condition is present for longer than 15 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and tailed.
^ The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL Off during the third consecutive trip in which the diagnostic has run and passed.
^ The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids
Inspect for the following conditions:
^ A faulty connection at the PCM or the IAC motor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections.
^ A damaged harness. Inspect the wiring harness for damage.
^ A restricted air intake system. Inspect for a possible collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.
^ The Throttle body. Inspect for objects blocking the IAC passage or the Throttle bore, excessive deposits in the IAC passage and the IAC pintle, and excessive deposits in the Throttle bore and on the Throttle plate.
^ A large vacuum leak. Inspect for a condition that causes a large vacuum leak, such as a incorrectly installed or malfunctioning crankcase ventilation valve or brake booster hose disconnected.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
10. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.