Error code

OBD2 P0505

OBD2P0505
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Idle Air Control System.

Severity

moderateCan drive but may experience stalling and poor performance.

Summary

P0505 indicates an issue with the Idle Air Control (IAC) system, which helps maintain proper engine idling speed.

Symptoms

  • Stored trouble code and illuminated warning light
  • Fluctuations in idle speed
  • Higher or lower than specified idle speed
  • Engine stalling unless accelerator is pressed

Common Causes

  • Carbon build-up in the throttle body or IAC valve air passages
  • Defective wiring, connectors, or circuits
  • Faulty idle air control valve
  • Failed step motor
  • Charging system issues (specific to some GM/Dodge vehicles)

Diagnosis

  1. Check for other codes and address them in order of storage
  2. Inspect vacuum system for leaks
  3. Clean or replace throttle body and IAC valve if heavily carbonized
  4. Inspect wiring for damage, corrosion, or shorts
  5. Perform resistance checks on signal wire between PCM and stepper motor

Fixes

  • Cleaning the throttle body and IAC valve passages with approved cleaner
  • Replacing faulty idle air control valve or step motor

FAQ

What causes P0505?

Common causes include carbon build-up, wiring issues, and defective components like the IAC valve or step motor.

How do I clean the throttle body?

Use an approved cleaner to remove carbon deposits from the throttle body and auxiliary air passages.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

More OBD2 codes

All OBD2 codes →Search more codes →