Finding what error code means on '98 F150

I have a 1998 F150 V6. My check engine light is on and I used one of those obn error code checkers. It had two error codes. P0171, Bank 1 too lean. P1506, didn't give what this error is. What are these errors and how do I correct them? Aslo where would I go to find what these errors are?

Thanks,
Gary

P1506 Idle Air Control System Overspeed Error

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


Hope this helps

The po171 is a lean (left rear bank i believe) dtc code. A lot of people replace the o2 sensor when this code flies. Before you do that, make sure you check for vacuum leaks above the intake plenum. I had the same code, and sure enough it was a vacuum leak. And if it is an o2 sensor, be very careful when removing the old one. The threads can strip very easily, and tapping the hole in the catalytic converter is a real pain when it is still on the truck. Some people will say warm up the truck and let it cool before replacing the o2 sensor, but I have always had better luck when it is cold.

I was checking the IAC valve as vet suggested. I pull it off and there was a little crud on the inside but there is a plastic piece inside the throttle body that looks like a cover of sorts. I tried to take it off to see if it needed cleaning but it wouldn't come out easily so I didn't try very hard. Is that suppose to come off? Is there a check to see if that is operating properly?

Thanks