Bad idle air control valve triggers Check Engine light

Your car’s “Check Engine” or “Service Engine Soon” light can flash on for more than 1,400 different reasons, and in the coming months, we’re going to share with you what some of those reasons are. The light is part of your vehicle’s on-board diagnostics (OBD) system and can indicate anything from a quick fix like a loose gas cap to a major repair like a catalytic converter.

Trouble code: P0505 IAC Malfunction

This code refers to the idle air control valve, which controls the idle speed of your engine—such as when you’re sitting at a red light. The idle air control valve is controlled by a computer, which allows a certain amount of air around the throttle plate and controls the idle speed. The powertrain control module uses the IAC valve to keep the vehicle idling at the proper speed.

Symptoms of a P0505 IAC Malfunction may include:

• Check engine light would illuminate

• The engine stalls and may not idle unless the gas pedal is depressed

• The vehicle intermittently stalls when letting off the gas pedal

• The engine may idle too high

Potential causes of a P0505 code include:

• The IAC motor connector is damaged

• One or more IAC circuits is open or shorted to ground

• One or more IAC circuits are shorted to voltage

• The IAC has failed

• The PCM has failed