DTC P0507: Idle Control System, Rpm Greater Than Expected: Condition

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when actual engine speed is 200 RPM greater than programed target speed for more than 14 seconds with brake pedal depressed and front wheels in straight ahead position (power steering pressure switch is off). This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are:

Accelerator cable misadjustment.
Cruise control actuator cable misadjustment.
Idle Air Control (IAC) valve malfunction.
PCM malfunction.
Throttle valve malfunction.
Vacuum hoses misrouted.