P0505

DTC P0505 Idle Control System (1 Of 2):

DTC P0505 Idle Control System (2 Of 2):

Idle Control System:

CIRCUIT DESCRIPTION


The Engine Control Module (ECM) controls the Idle Air Control (IAC) valve to regulate the air bypass passage. The amount of the opening determines the idle speed. The IAC valve is regulated according to engine load. A stalling condition could be caused by the IAC 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 ECM 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.

- DTC(s) can be cleared by using a scan tool or by disconnecting the ECM 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 the following conditions:

- Idle adjustment procedure.

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

- Damaged harness. Inspect the wiring harness for damage.

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

- Throttle body. Check for objects blocking the IAC passage or throttle bore, excessive deposits in the IAC passage and on the IAC pintle, and excessive deposits in the throttle bore and on the throttle plate.

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


TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Engine 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. If idle speed is out of specifications, refer to idle speed adjustment procedures.

4. 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 ECM.