P0506: Idle control system RPM lower than expected
The engine idles slower than the engine computer is aiming for, and it can’t bring the speed up. The engine may stall at idle.
Updated
What P0506 means
At idle, the engine computer sets a target speed and controls the air that gets past the closed throttle to hold it: with an idle air control valve on older engines, or with the electronic throttle on newer ones.
P0506 means the engine idles slower than the target, and the computer can’t bring it up. With too little air at idle, the engine can stumble or stall, for example when you stop or when the air conditioning switches on.
Read My Car’s live data shows the engine speed, so you can see the idle speed directly.
P0505: idle control system
P0505 is the general idle control fault: the idle is too high, too low or hunts up and down, and the computer can’t correct it. On older engines it often points to the idle air control valve. An idle that’s only too high is P0507, which has its own page.
P0505: Idle control system malfunction
The engine computer can’t hold the idle speed where it wants it: the idle is too high, too low or hunting, and the engine may stall.
Common causes: dirty or sticking idle air control valve, dirty throttle body, vacuum or intake air leak.
Can I keep driving?
Drive gently
Drive gently and have it checked soon. The engine can stall when you slow down or stop, and steering and braking then get much heavier until it restarts, so leave extra room in traffic.
General guidance based on the code alone, not on the car’s actual condition. If in doubt, stop and ask a mechanic.
If the engine stalls, steering and braking get much heavier until it restarts: brake and steer with more force, and leave extra room at junctions and in traffic.
Symptoms
- The idle speed is lower than usual, or rough and uneven.
- The engine stalls when you stop or slow down, or when the air conditioning switches on.
- With P0505, the idle may also hunt up and down, or sit too high.
Common causes
- Dirty throttle body. Carbon around the closed throttle plate narrows the gap the idle air flows through.
- Dirty or sticking idle air control valve. On engines that have one, a valve stuck nearly closed lets in too little air.
- Restricted air intake or a crankcase ventilation (PCV) fault. Less often: a blocked intake or a PCV fault changes the air the engine gets at idle.
Typical fixes
- Have the throttle body and, if there is one, the idle air control valve cleaned.
- On many cars with an electronic throttle, the idle has to be relearned after cleaning. The service information for your car describes how; some cars need a tool for your make for it.
- Check the air filter and the intake for blockages, and the crankcase ventilation (PCV).
- For P0505, also check for vacuum leaks, and replace the idle air control valve if cleaning doesn’t help.
- Clear the code and watch the idle speed in live data.
Questions
Can I drive with P0506?
Gently, and have it checked soon. The engine can stall when you slow down or stop, and steering and braking then get much heavier until it restarts, so leave extra room in traffic.
Can cleaning the throttle body fix P0506?
Often, if carbon is the cause. On many cars with an electronic throttle the idle then has to be relearned, as the service information for your car describes.
What is the difference between P0505, P0506 and P0507?
P0506 is an idle that’s too low, P0507 one that’s too high, and P0505 a general idle control fault. A low or unstable idle can stall the engine, which is why P0505 and P0506 get “Drive gently” and P0507 “Check soon”.