CEL Codes

PO421
The catalytic converter is no longer functioning properly
An oxygen sensor is not reading (functioning) properly
A spark plug is fouled.
Time to have the O2 sensor after the cat tested. It should show steady voltage (~200MV depending on the vehicle). If the voltage varies (100MV to 600MV) it is time to replace the cat. Have all the O2 senors tested while your at it.

P1506 Idle Air Control System Overspeed Error (Ford)
This DTC is set when the PCM detects engine idle speed that is greater than the desired rpm.
Causes.
IAC circuit short to GND
Damaged IAC valve
IAC valve stuck open
Vacuum leaks
Failed EVAP system


I would start out by cleaning the IAC valve and it's port.

Good luck and let us know.

Hi when I look at this unit, it has two screws that look like TORX screws, but my torx wrenches won't work due to the srcew has a small spot in the middle which will not allow the torx wrench to fit into it, unless it is the phillips head screws I see on the unit,,, I just figured I would ask before I started ripping it apart
any ideas?

10 year old screws can be a pain. My guess is that they are torx but with some corrosion in the center. Clean them out with a nail head or scratch awl tip. Use a magnifying glass if you are still uncertain as to their type. What unit are you removing?