Idle speed control

What it means

The computer holds the engine at a steady idle speed, whatever the load from air conditioning, lights and steering. These codes mean the real idle speed is not close to the target, or the idle control valve circuit is faulty.

Codes in this group

Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.

What you may notice

• Idle too high or too low
• Idle hunting up and down
• Stalling when stopping or when the air conditioning switches on

Common causes

Most likely first:

• A dirty throttle body or idle air valve
• A vacuum leak (high idle)
• A failed idle air control valve on older cars
• A throttle that needs a relearn after battery disconnection or cleaning

What to check first

• Check for a floor mat or cable holding the throttle slightly open
• Listen for a hiss from a vacuum leak
• Cleaning the throttle body is a common, low-cost fix

Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.

After the repair

Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.

Related codes

Engine overheating or overspeed (P0217), Fuel level sensor (P0460), Radiator cooling fan circuit (P0480), Vehicle speed sensor (P0500), Brake pedal switch (P0504), Engine oil pressure sensor (P0520), Air conditioning pressure sensor (P0530), Battery and charging voltage (P0560). All codes.

Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.