What does P0505 mean?
The control module detected a condition described as “Idle-air control system – malfunction”. The code identifies the affected area, but it does not by itself prove which component has failed. The code describes the detected condition, not a guaranteed failed part. A reliable diagnosis also considers related codes, freeze-frame data, live values and the actual symptoms.
Possible causes
- Intake leak or unmetered air
- Contaminated mass-air-flow sensor or throttle body
- Faulty MAP, MAF or throttle-position sensor
- Broken wiring, poor contact or incorrect adaptation
Common symptoms
- Fluctuating or high idle speed
- Poor throttle response and power loss
- Hesitation or engine stalling
- Limp mode
Sensible next checks
- Inspect intake and vacuum hoses for cracks
- Compare MAF, MAP and throttle-position live data
- Check connectors and supply voltages
- Perform adaptation after cleaning or repair when required
Why does it return after clearing?
Clearing the code only removes the stored entry. If the underlying condition remains, the control module will set the code again after the next relevant monitor cycle. Save the data first, diagnose the cause, repair it and only then clear the code.