P0507: Idle Air Control System RPM Higher Than Expected

What P0507 tells you, and what it does not

Idle speed settles above the target the computer is trying to reach, which can make the vehicle creep forward when the brake is released in gear.

The code sits in the idle speed control area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Idle sits noticeably higher than normal
• Vehicle creeps forward at stops in gear
• Engine revs high after starting and does not settle
• Fuel economy drops slightly

What causes P0507?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a idle speed control fault becoming an expensive guess.

Vacuum leak drawing in unmetered air is the one to rule out before anything else. This is the most common cause of an idle that will not come down.

Working out which cause it is

Start with freeze frame. Check the idle RPM stored when the code set compared to the target idle RPM. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

Diagnosing this one properly means commanding a component and watching whether it responds, which a read-only tool cannot do at any price. Commanding the idle air valve toward closed while watching RPM shows whether the valve or a vacuum leak is holding idle up.

The order worth working in

• 1. Vacuum leak drawing in unmetered air: This is the most common cause of an idle that will not come down.
• 2. Idle air control valve stuck open: A stuck valve keeps adding air even when the computer commands less.
• 3. Throttle plate not seating fully from carbon buildup: Deposits can prop the throttle open slightly at idle.
• 4. Sticking throttle or cruise control cable: A cable with a hint of drag can hold the throttle open a little at idle.
• 5. Leaking brake booster hose or other aftermarket vacuum connection: A leak at an accessory hose behaves just like a leak in the intake itself.

What P0507 means for driving the car

A high idle can make the vehicle creep forward unexpectedly in gear when the brake is released, so keep a firm foot on the brake at stops until this is fixed.

This is a severity 2 of 4 code. It will not usually strand you, but it will fail an emissions test while it is present, and the underlying fault rarely gets cheaper by being left alone.

What does it cost to ignore P0507?

A high idle wastes fuel continuously and creates a real creep hazard at every stop until it is fixed.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.