EN

Severity: Low Code type: Manufacturer-specific (Ford)

Ford P1506 Code: Idle Air Control Overspeed Error

Ford's idle speed stays above target even though the PCM has closed the idle air valve as far as it can.

At a glance

Severity: 2/5 – Low2/5

Severity: Low

Meaning
Idle Air Control Overspeed Error
System
Speed & Idle Control · Powertrain
Safe to drive?
Yes, short term
Typical repair cost
$20–$700
DIY difficulty
Moderate

On Fords with a throttle cable and a separate idle air control (IAC) valve, the PCM sets a target idle speed and opens or closes the IAC bypass to hit it. P1506 means the engine keeps idling faster than that target while the PCM is already commanding the IAC toward minimum, so extra air must be getting in somewhere else. The usual suspects are an intake vacuum leak, a throttle plate that isn't returning to its stop, or an IAC valve that leaks air even when commanded shut. It appears on EEC-V era trucks and cars such as the F-150, Ranger, Explorer, Mustang and Taurus; newer Fords with electronic throttle report idle problems with generic codes instead.

Can I keep driving? The car is drivable, but a high idle makes automatics creep hard against the brake and wears brakes faster. Fix it soon, and treat a hissing vacuum leak as the priority.

How to read P1506

How to read P1506P11253064
  1. P Powertrain
  2. 1 Manufacturer-specific
  3. 5 Speed, idle & inputs
  4. 06 Specific fault

Symptoms

  • Idle sits noticeably high when warm, often 1,000 rpm or more
  • Automatic pulls hard in Drive at a stop; manual cars are slow to drop rpm when you press the clutch
  • Hissing or whistling from the intake area
  • Lean codes P0171 and P0174 when the extra air comes from a vacuum leak
  • Idle hangs or surges when coasting to a stop

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. Vacuum leak after the MAF sensor: cracked intake boot, PCV hose, brake booster line or intake gasket 35%
  2. Throttle not returning fully: sticky throttle or cruise cable, bent linkage, tampered stop screw 20%
  3. IAC valve stuck partly open or leaking air when commanded closed 20%
  4. PCV valve stuck open or wrong PCV valve fitted 10%
  5. Idle adaptation lost after battery disconnect and not relearned 10%
  6. Coolant temperature sensor reporting a cold engine, raising the target idle 5%

Diagnosis step by step

Diagnostic flow: P15061Compare actual and desired idle2Unplug the IAC at idle3Check that the throttle closes4Hunt for vacuum leaks5Test the IAC valve6Relearn idle after the repair

  1. Compare actual and desired idle

    At full operating temperature, read RPM, desired RPM and IAC duty cycle. If RPM is far above desired while the IAC command sits near its minimum, the PCM has run out of authority and air is entering elsewhere.

    Tools: OBD-II scanner

  2. Unplug the IAC at idle

    With the engine warm and idling, disconnect the IAC valve. On a healthy system idle should drop sharply or the engine may nearly stall. If idle barely changes, the extra air isn't coming through the IAC.

  3. Check that the throttle closes

    Engine off, watch the throttle lever snap back against its stop. Look for a sticking cable, a cruise control cable pulling slightly, or a floor mat holding the pedal. Don't adjust the factory stop screw to hide a leak.

    Tools: Flashlight

  4. Hunt for vacuum leaks

    Smoke-test the intake with the engine off, or listen at idle for hissing around the intake boot, PCV hoses and brake booster line. Also check that long-term fuel trims aren't strongly positive, which confirms unmetered air.

    Tools: Smoke machine, OBD-II scanner

  5. Test the IAC valve

    Most Ford IAC valves are two-wire solenoids measuring roughly 6 to 13 ohms. Remove it and check that the plunger closes the bypass fully; a sticky or carbon-bound valve may hang open.

    Tools: Multimeter, Screwdriver

  6. Relearn idle after the repair

    Clear codes, start the engine without touching the pedal and let it idle for a couple of minutes, then another minute with the A/C on. Drive a short loop so the PCM can store its new idle values.

    Tools: OBD-II scanner

Where the parts are

Air intake and fuel metering – P150612345678
Air intake and fuel metering
  1. 1MAF sensor
  2. 2Turbocharger
  3. 3Throttle body
  4. 4Intake manifold
  5. 5Fuel injector
  6. 6EGR valve
  7. 7Fuel pump
  8. 8Thermostat

Repair options & costs

RepairDIY?Estimated cost
Replace cracked intake boot, PCV or vacuum hose Yes $20–$180
Free or replace sticking throttle or cruise cable Yes $40–$200
Replace IAC valve Yes $80–$280
Replace intake manifold gasket No $250–$700
Replace coolant temperature sensor Yes $60–$180

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Emissions / smog test impact

Will fail

P1506 turns on the check engine light on most applications, so an OBD emissions test fails. A vacuum leak that causes it can also trigger lean codes, which must be cleared and the monitors completed before retesting.

Frequently asked questions

Why is my Ford idling high with P1506?

The PCM has already closed the idle air valve, yet the engine still gets too much air. That extra air almost always comes from a vacuum leak, a throttle that doesn't fully close, or an IAC valve that leaks when shut.

Can I turn the throttle stop screw to lower the idle?

No. That screw is set at the factory and adjusting it upsets the PCM's idle learning and the throttle position reading. Find the source of the extra air instead.

Does P1506 have anything to do with P1507?

They're opposites. P1506 means idle is too fast and the IAC can't pull it down, while P1507 means idle is too slow and the IAC can't raise it. Seeing both usually points to an erratic IAC valve or a loose connection.

Will cleaning the throttle body fix P1506?

Rarely. Carbon usually makes idle drop, not climb. Cleaning helps only if deposits are keeping the throttle plate or IAC plunger from closing.

Sources