Idle Air Control Overspeed Error (Ford)
What does P1506 mean?
The P1506 code means the vehicle's onboard diagnostic system has detected: Idle Air Control Overspeed Error (Ford). This is a moderate severity code.
Common Symptoms
- Engine idle speed too high (over 1200 RPM)
- Check Engine Light illuminated
- Engine revs up when coming to a stop
- Creeping forward when stopped in gear
- Difficulty slowing the vehicle at stops
Probable Causes (Ranked by Likelihood)
- Vacuum leak at the intake manifold or hoses Very High
- Stuck-open IAC valve High
- Throttle cable or linkage holding the throttle partially open Moderate
- Dirty throttle body with deposits holding the plate open Moderate
- Faulty throttle position sensor reporting incorrect position Low
Step-by-Step Diagnostic Procedure
-
Check for vacuum leaks at the intake manifold gaskets, vacuum hoses, PCV valve, and brake booster line.
-
Inspect the IAC valve for sticking. Remove it and verify the pintle moves freely.
-
Check the throttle cable for binding or excessive tension that prevents the throttle from fully closing.
-
Clean the throttle body bore and plate edges to remove carbon deposits.
-
Verify the TPS reads close to 0.5V at closed throttle with the engine off.
Frequently Asked Questions
Why is my idle so high?
Extra air is entering the engine past the throttle plate, either through a vacuum leak, a stuck IAC valve, or a throttle plate that is not fully closing. The engine speeds up because the PCM cannot reduce air intake enough.
Is high idle dangerous?
A high idle increases fuel consumption and can cause the vehicle to creep forward when stopped in gear. While not immediately dangerous, it should be repaired to prevent unsafe driving conditions and excessive wear.
Can a vacuum leak really raise the idle by that much?
Yes. A significant vacuum leak at the intake manifold gasket or a large disconnected hose can easily raise idle speed by 500 RPM or more. Smoke testing is the most effective way to find these leaks.