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This is tough one to search on. Most of the results talk about a poor idle or the high idle mod.
I simply have no cold idle up. It used to work a few years ago but doesn't anymore. I live in Colorado and it's definitely cold enough for the high idle to kick in.
I have no codes, nothing bad shows up on the Auto Enginuity.
I don't know what the PCM is watching to decide on idle rpm but it seems doubtful it's a software issue (just thinking out loud). It may watch IAT1 or IAT2 along with oil and coolant temps. Does it use the PTO idle box (what ever we call it ) that responds to the high idle wiring under the dash?
I believe your right Iat2 and Maff, looking at Ambient temps, Maff looks at air fuel timing so if both are in the blue it kicks the EGR closed to heat up the Intake gasses , PCM notices the heat transfer via Sensors and Walla high idle more fuel ratio until heat is achieved .