P0506: the engine is idling slower than the computer wants
The idle air control system lets the engine control unit hold the engine at a steady idle speed without your foot on the accelerator, by controlling a small amount of extra air, or on many newer engines by moving the electronic throttle itself. This code means the actual idle speed is running lower than the computer is commanding, even after the system has tried to correct it. It doesn't say why the engine won't idle any faster, only that it isn't reaching the target.
You might notice
- The engine warning light comes on
- The engine may idle roughly or feel close to stalling at a standstill
- idle air control system
- — the system that holds the engine at a steady idle speed without your foot on the accelerator
What the code itself says
P0506 is a powertrain (engine, gearbox and drive system) code, and the 0 after the letter means it is a generic code with a standard meaning.
Grouped here as: Engine running, fuelling and misfires — Air metering, fuelling, ignition, misfire, idle, boost, knock, oxygen sensors and the catalyst, all working together in the running engine. That grouping is ours, to help explain the code. The code's official family is the letter at the start.
This page is generic. Your car isn't.
A code on its own only tells you what the sensor saw, not what's actually wrong — and that changes next to your other codes. Read this one together with the rest of your scan and we'll work out what's really going on.
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