First, I had the diode installed to the IAT sensor. Did this mod since it first came out. Had no problems with it until recently. The code just started the past couple of months. In the back of my mind I kept thinking it was related to the morning cold. Finally decided it was time to get rid of the engine code light from reappearing. Long story short, the wiring harness was in good shape. Figured the easiest way to see where the problem was  to put it back to stock. Been fine since. Amazing that a 10 cent part can change everything!

Ummm... Diode would crate that issue. Diode is nothing my than a check valve for power. It can only follow in one direction so if you hook it up one way you'll have hi volt code and reverse it and have lo volt code. But now a resistor of proper value should not trip any codes because the computer see the proper range of voltage.

Sorry! It was a resistor. I think that either the resistor was going bad, loose connection, or corrosion is the only thing I can think of.

More than likely... If the connection was poor and it gets out of range then the code will pop. But like myself I'm still using the MPG fooler yet. No issues.