What does P0505 mean?

The ECU cannot control the engine's idle speed properly.

Does cleaning the throttle body help?

Very often yes; carbon build-up around the throttle is a common cause.

Speed and idle control

P0505 — Idle Control System Malfunction

The ECU cannot keep the engine idle speed at the target value. The idle may be too high, too low or unstable.

Severity: Medium

Common causes

Dirty throttle body or idle air control valve
Vacuum or intake leak
Faulty idle air control valve or electronic throttle
Faulty throttle position or MAF sensor
Carbon build-up in the intake

Symptoms

Unstable, hunting idle
Stalling at stops
High idle speed
Check engine light

How to check

Clean the throttle body and idle air passages
Look for vacuum leaks
Check idle speed and the idle air control or throttle motor operation on a scan tool
Check throttle position and MAF readings

Can you keep driving?

Usually drivable, but stalling at stops can be unsafe in traffic. Repair it soon.

Frequently asked questions

What does P0505 mean?: The ECU cannot control the engine's idle speed properly.
Does cleaning the throttle body help?: Very often yes; carbon build-up around the throttle is a common cause.

General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.