P0506 — Idle Air Control System RPM Lower Than Expected

What it means

The measured idle speed stays below the target value, usually by more than 100 rpm, even though the idle control has opened its air path as far as it can. The engine is not getting enough air or is under too much mechanical or electrical load. It shows up as a rough, low idle, shaking at a standstill and stalling when the steering is turned or a heavy consumer is switched on.

Likely causes (most common first)

1. Throttle body and idle passage clogged with carbon and oil mist
2. Idle air control valve stuck in the closed position
3. Restricted air filter or a collapsed intake duct
4. Excessive load from a seizing alternator, air conditioning compressor or power steering pump
5. Late ignition timing, weak fuel pressure or clogged injectors
6. Low compression or worn camshaft timing on high-mileage engines

Can you drive with it?

Driving is possible but unpleasant, and stalling at low speed is likely, so repair without delay.