Fault codeP0505

MODERATE

Idle Control System Malfunction

What this code means

Idle Control System Malfunction.

P0505 is a generic code: it means the same thing on every make. P0505 belongs to family P05xx — Idle speed and vehicle speed control. Its page explains how to read a code and groups all its codes by part.

Idle speed control

At idle, the control unit adjusts the air entering the engine to keep a stable speed, whatever the load of the alternator, the air conditioning or the steering. It does so with an idle valve on older engines, or by opening the motorised throttle slightly on newer ones.

What you notice

Idle too low that makes the engine shake or stall, or too high, sometimes surging up and down.

How to check it

The classic causes are a dirty throttle body or idle valve and an air leak after the throttle. Cleaning followed by a relearn procedure often solves it. In Klaro, watch the engine speed and throttle position at idle, then switch on the air conditioning: the speed should dip briefly and recover.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

Engine RPM
Throttle position
Calculated engine load

What to do

Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.

Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →

How to read this code

PPowertrain
0standardised code
5Idle speed and vehicle speed control
05P0505