P0505

DTC P0505

CIRCUIT DESCRIPTION
The DTC P0505 Idle Air Control (IAC) System diagnostic observes engine speed in order to monitor the operation of the IAC valve. The powertrain control module (PCM) controls engine idle speed with the idle air control valve. To increase the idle speed, the PCM pulse width modulates the OPEN solenoid within the IAC valve. This action turns a cylinder within the IAC valve, allowing air to bypass the throttle plate. The PCM regulates fast idle speed via the IAC valve by increasing the opening of the air bypass port. The PCM regulates slow idle speed via the IAC valve by decreasing the opening of the air bypass port.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0505 Idle Air Control (IAC) System

CONDITIONS FOR RUNNING THE DTC
- DTCs P0011, P0012, P0031, P0032, P0100, P0101, P0102, P0103, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0130, P0133, P0134, P0171, P0172, P0300, P0301-P0304, P0335, P0340, P0341, P0351-P0354, P0385, P0500, P0850 are not set.
- The battery voltage is more than 11 volts.
- The engine coolant temperature is at least 75°C (167°F).
- The engine is running.
- Vehicle speed is less than 3 km/h (1.8 mph).
- DTC P0505 runs continuously once the above conditions have been met.

CONDITIONS FOR SETTING THE DTC
The observed engine speed at idle is less than the expected engine speed by 100 RPM or more.

OR

The observed engine speed at idle is more than the expected engine speed by 150 RPM or more.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs with the fault active.
- The PCM stores the conditions which were present when the DTC set as Freeze Frame data.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
- A DTC can be cleared by using the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS
With the engine idling at a normal operating temperature and all accessories OFF, monitor the following parameters on the scan tool for correct operation:
- The IAC Motor Command-27-43 percent
- The electrical load-No
- The commanded A/C-OFF

The scan tool can be used to isolate the cause of an intermittent DTC P0505. Engine idle speed can be controlled with the scan tool. Operate the IAC valve with the scan tool while checking for a smooth increase and decrease in engine speed. If engine speed can be controlled, the IAC system is functioning normally.

Check for the following conditions:
- Any blockage of the air intake system
- Any blockage of the IAC passage
- Excessive deposits on the throttle plate or the throttle bore
- Any large vacuum leaks

An intermittent malfunction may be caused by a fault in the IAC sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions

Repair any electrical circuit faults that were found.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

If the DTC P0505 does not reset, but a driveability symptom still exists, refer to Symptoms - Computers and Control Systems. Symptom Related Diagnostic Procedures

TEST DESCRIPTION

Steps 1 - 8:

Steps 9 - 13:

The numbers below refer to the step numbers on the diagnostic table.
6. This step simulates the pulse width modulated (PWM) signal supplied to the IAC valve by the PCM by rapidly grounding and un-grounding terminal 1 of the IAC valve.
8. The most likely cause of no power is an open circuit condition between the IAC valve connector terminal 2 and the splice. A shorted or inoperative EFI relay circuit will cause a no-start condition.