P0506

Idle Air Control (IAC) Circuit:

Circuit Description
The Powertrain Control Module (PCM) controls the air entering into the engine with an Idle Air Control (IAC) valve. To increase the idle rpm, the PCM commands the pintle inside the IAC valve away from the throttle body seat. This allows more air to bypass through the throttle blade. To decrease the rpm the PCM commands the pintle towards the throttle body seat. This reduces the amount of air bypassing the throttle blade. A scan tool will read the AC valve pintle position in counts. The higher the counts, the more air that is allowed to bypass the throttle blade.

Conditions for Setting the DTC
- The IAC valve reads greater than 145 counts on the scan tool.
- The barometer is greater than 72 kPa.
- The Engine Coolant Temperature (ECT) sensor indicates temperature greater than 40°C.
- The idle speed deviates below desired rpm by greater than 60 rpm for greater than 5 seconds.
- The engine run time is greater than 20 seconds.
- The battery voltage is between 10 and 17 Volts.
- The Throttle Position (TP) angle is less than 1%.
- One or more of the following DTCs are not set: P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0l32, P0133, PO134, P0335, P0341, P0342, P0502, P0503, P0562, P0563, P0600, P1133, P1520.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
- The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn "OFF" after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- DTCs can be cleared by using a scan tool.

Diagnostic Aids
- Inspect the IAC valve electrical connection for proper mating.
- Inspect the wiring harness for damage.
- Inspect the throttle stop screw for signs of tampering.
- Inspect the throttle linkage for signs of binding or excessive wear.
- A slow, or unstable idle may be caused by one of the following conditions:
- Fuel system to rich or to lean.
- Foreign material in the throttle body bore or in the air induction system.
- A leaking or restricted intake manifold.
- Excessive engine overloading. Check for seized pulleys pumps, or motors on the accessory drive.
- To high a viscosity engine oil.

- Refer to Rough, Unstable or Stalling in Diagnosis By Symptom.

Symptom Related Diagnostic Procedures

DTC P0506 - Idle System Low - IAC Responding (1 Of 2):

DTC P0506 - Idle System Low - IAC Responding (2 Of 2):

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. The OBD System Check prompts the Technician to complete some basic checks and store the Freeze Frame Data and the Failure records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
9. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.