P0505 Subaru Outback
Idle Air Control System Malfunction · Powertrain Code · Medium · Repair: Easy
What is P0505?
The idle air control (IAC) system is not maintaining proper idle speed.
When the Subaru Outback triggers code P0505 (idle air control system malfunction), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Subaru Outback.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Subaru Outback.
Common Causes on Subaru Outback
- Dirty or failed idle air control valve (older EJ engines)
- Carbon buildup in electronic throttle body (FB engines)
- Vacuum leak disrupting idle air control
- Failed idle speed control system
Symptoms
- Check Engine Light on
- Unstable idle speed
- Idle too high or too low
- Stalling at stops
- Hunting idle
Notes for Subaru Outback
After cleaning the throttle body, disconnect the battery for 60 seconds to force an idle relearn on Subaru models.