What does Code P1506 mean on a Ford Taurus?

Answer 1

P1506 IAC OVERSPEED

This code denotes that the IAC is causing the motor to have an excessively high idle. This maybe caused by a vacuum leak, the IAC being unplugged or the wiring compromised, the IAC failing to maintain proper idle speed, or the IAC Failing entirely. Typically the IAC (Idle Air Control Valve) has failed or is jammed open due to carbon build up inside of the valving, and the solenoid is not able to move the valving properly.

First ensure there is no vacuum leaks to the intake plenum. It is quite likely it is indeed the IAC valve, but to rule out an erroneous code (and keep you from paying for a new IAC without need) it is good to make sure none of the vacuum lines are leaking or broken. The rationale behind this is the IAC may be closed entirely and the engine speed is above normal allowances, and since the IAC is closed, the computer may think that the IAC is stuck open. The IAC on this vehicle is dumb and pulsated through electrical pulses. It opens and closes rapidly to maintain engine idle. (Hence the 2 wire connection. It is either on or off and does not have any logic circuitry built into it to determine whether or not it is on or off. The PCM only knows that it is telling the IAC to open or close, but does not know if it is open or closed.)

To check your IAC valve, locate your valve, it's location may differ on weather or not it is the 3.0L DOHC V6 Duratec, or the 3.0L OHV Vulcan engine. On the Vulcan it is located toward the back of the intake plenum directly adjacent to the throttle body. You can tap it with a hammer (lightly) to see if this assists the problem, if not it's quite likely your IAC is At Fault.