P0505

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The Powertrain Control Module (PCM) controls the Idle Air Control (IAC) valve to regulate the air flow through the idle air bypass passage. The amount of air flowing through the idle air bypass passage determines the idle speed. The IAC valve is regulated according to engine load A stalling condition could be caused by the AC valve not functioning properly.

Conditions for Setting the DTC

- Difference from target speed is 100 RPM lower than target value.

- Difference from target speed is 200 RPM greater than target value.

- Engine coolant temperature is between 70°C (158°F) and 110°C (230°F).

- Intake air temperature is between -7°C (19°F) and 70°C (158°F).

- Barometric pressure is greater than 75 kPa.

- In closed loop.

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 buffer.

Conditions for Clearing the MIL/DTC

- The MIL will turn off after three consecutive drive cycles without a fault present.

- A DTC will clear after 40 consecutive warm-up cycles without a fault.

- The DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

Diagnostic Aids

Check the IAC duty and idle speed by using IAC CAL under Misc. test (IAC Duty Flow - 50% and Idle Speed = 800 rpm 50 rpm.

Check for any of the following conditions:

- An incorrect engine idle speed. Refer to On-Vehicle Service in Fuel Metering.

- A poor connection at the PCM or IAC valve. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal to wire connection.

- A damaged wiring harness. Inspect the wiring harness for damage and repair as necessary.

- A restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element, or foreign objects blocking the air intake system.

- Inspect the throttle body for the following:

- Check for objects blocking the IAC passage or throttle bore.

- Check for excessive deposits in the IAC passage or on the IAC pintle.

- Check for excessive deposits in the throttle bore or on the throttle plate.

- A large vacuum leak. Check for a condition that causes a large vacuum leak, such as a incorrectly installed or faulty crankcase ventilation valve or a disconnected brake booster hose.

Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain (OBD) System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks for the correct IAC Duty reading. If the IAC Duty is out of specification, the idle speed will need to be checked.

3. This step checks for the proper engine idle speed. Refer to On- Vehicle Service in Fuel Metering. If the engine idle speed is within specifications (or was previously adjusted to specifications), go to the NO response and continue diagnosis.

5. Measure the resistance of the IAC valve.

6. This test checks the functionality of the IAC valve. If the IAC valve operates accordingly, the malfunction may be the cause of the IAC valve control circuit or PCM.