Hey Guys, I posted a while back with some "issues" I was having after I installed The Hughes air gap intake manifold and big gulp throttle body. My "problem" was not being able to start it. As it turned out, someone had siphoned my gas tank dry. Well, I put a locking cap on it, and haven't had that problem happen again. The truck has been running pretty damn good. Only issue I have is the check engine light will not go off. The code is P0505. Idle Air Control System. I had gotten the sct tuner for it so that when I got my stroker in, I could program it to the stroker mods. I did not get the program for the stroker though. Im gonna do that once the stroker is in it. I got the programs just to take advantage of the current mods. So I can plug in the tuner and get the code, then I can clear the code. But as soon as I start the truck, it comes back on. I have tried replacing the I.A.C. sensor from autozone, oreillys, and advanced auto. All of them made the truck run very rough, or at very high idle. I put the original one back in and it runs almost perfect. There is a very slight variation in the idle (like from 800 to 1100). Barely noticeable. But I cant pass inspection with that damn check engine light on. Also noticed that when Im cruising along and get into the throttle, it gains speed beautifully. But if Im in like 2nd gear and I mash on it, it takes a few seconds to get up and go. Not sure what my issue is here. Hopefully one of you guys has an idea what my problem is. My truck is a daily driver and it gets up and goes every day. Its just this little hiccup I need to address, as my inspection runs out the end of July. Any suggestions are very much appreciated.

 

P0505 is a right pain to troubleshoot, and solve.

The IAC uses to circuits, four wires. The are both individually controlled by the PCM. The PCM 'steps' the IAC by applying voltage (and ground on the other side of the circuit) to run the stepper motor (IAC). So, with the engine running, you should see 12 volts on two of the wires..... (when the engine gets to desired idle, the PCM will apply power to both circuits, to lock the iac in place.)

I *think* there is a thread in the FAQ section for troubleshooting IAC issues, but, given you have gone thru three of them, I don't think it's the IAC that's the trouble, it's either going to be wiring, or the PCM.