So to begin, I have read every forum post I can find on google and on this site about this issue. I have also tried every "fix" that people had suggested on those post before finally posting this one. The truck is a 2005 F150 with the 4.6L motor. It has about 113,000 miles on it. It has not had any problems until now. It would die sometimes when switching gears from forward to reverse etc. Acouple of days after that started, I got the CEL. Pulled the code P0506 (Idle air control system RPM lower than expected)
Idle Air Control System RPM Lower Than Expected

Read more at: http://www.obd-codes.com/p0506
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Idle Air Control System RPM Lower Than Expected

Read more at: http://www.obd-codes.com/p0506
Copyright © OBD-Codes.com
Idle Air Control System RPM Lower Than Expected

Read more at: http://www.obd-codes.com/p0506
Copyright © OBD-Codes.com
It started to idle rough, the rpms would bounce around from 400-700 with the air conditioning on. With the AC off, it was fine. 1st thing I did was take the throttle body off and clean it. It was pretty nasty, and looked like it had never been cleaned. The back side of it was completely black. Afterwards I put it back in and started the truck. The truck would barely start and idle. The CEL cleared and did not come back, but the wrench light came on. There is no response from the gas pedal. I changed the throttle position sensor, just in case that got messed up somehow. Afterwards it was the same thing, nothing changed after replacing the TPS. So where I am at now is the wrench light is on and the truck idles normally, but I cant get the wrench light to clear. Ive disconnected the battery more than once, cleaned the terminals, checked all the fuses and relays. I am starting to think maybe the PCM is fried? I do not understand how when it would run and drive before I took the throttle body off and cleaned it. Any input or ideas would be greatly appreciated at this point.

 

My wrench light came on after cleaning the throttle body because the intake boot had slipped off after start up.

 

The throttle body mounting gasket may need replacing. They're pretty cheap (under $5) and can found at most auto stores.

 

1) Check for exhaust restriction (clogged cat?) else
2) Replace throttle body.

 

Did you resolve the problem? And how? I have exactly the same thing happening right now

Read more at: http://www.obd-codes.com/p0506
Copyright © OBD-Codes.com
Idle Air Control System RPM Lower Than Expected

Read more at: http://www.obd-codes.com/p0506
Copyright © OBD-Codes.com
Idle Air Control System RPM Lower Than Expected

Read more at: http://www.obd-codes.com/p0506
Copyright © OBD-Codes.com
It started to idle rough, the rpms would bounce around from 400-700 with the air conditioning on. With the AC off, it was fine. 1st thing I did was take the throttle body off and clean it. It was pretty nasty, and looked like it had never been cleaned. The back side of it was completely black. Afterwards I put it back in and started the truck. The truck would barely start and idle. The CEL cleared and did not come back, but the wrench light came on. There is no response from the gas pedal. I changed the throttle position sensor, just in case that got messed up somehow. Afterwards it was the same thing, nothing changed after replacing the TPS. So where I am at now is the wrench light is on and the truck idles normally, but I cant get the wrench light to clear. Ive disconnected the battery more than once, cleaned the terminals, checked all the fuses and relays. I am starting to think maybe the PCM is fried? I do not understand how when it would run and drive before I took the throttle body off and cleaned it. Any input or ideas would

 

I am hoping you have gifted out what the issue was and could pass it along. I have exactly the same issue, replaced my throttle body and now I have a wrench light and no throttle. I also ended up replacing the pedal sensor as well.

 

Usually when you replace those sensors you have to calibrate them. Have you tried that?

 

Ended up being the return spring on the actuator. I followed the directions and they were WRONG. It told me to install the actuator/motor then use the plastic tool to turn the spring lock clock wise to set tension on the flap. Well it was forcing the flap to stay open more than idol and the cpu was going into limp mode. As soon as I adjusted the spring tension counter clockwise and closed the flap, the wrench went off and it's all good again.