Here's one that some may or may not know about Chevy's & the dreaded Check Engine Light. Mine came on the other day after we had lows of -28F or so then a 'heat wave' of +2F with rain etc etc for a couple days. The light came on, I pull over, pop the hood look for lose wires/connectors, everything seems OK, truck is idleing about 100rpm less than normal for it being warmed up. Nothing too odd, so I ask a buddy at work the next day, he said pop the gas cap off & then back on again... WTF?! yeah! It seems Chevy caps are prone to plugging from excess moisture/humidity/condensation & freezing, that creates a vaccuum in the tank & fuel system causing a Check Engine Light because of a low fuel pressure. Unfortunatelly when I tried this the light stayed on, so it's off to get it scanned after work today.

 

To the best of my knowledge 'low fuel pressure' does not set the CEL. After you get the code read, come back to this thread and let us know what it was and we'll see if we can help.

 

Same information you posted in another thread... Kind of off topic in the other thread...

Anyway, gas caps can and do go bad... This is the first I have heard of them freezing up though, living in NY working on GM vehicles for many years...

 

A lot of cars and truck have an issue with that, but its more due if the fuel cap is not on or seated correctly. I believe the the system is sealed, so that would cause that also. But I don't see why it would cause low idle, etc. You should get that read.

 

yeah it was off topic in the other thread, my bad so I moved it here... I'll post what the code was, hopefully just a MAF sensor dirty... I have a K&N Air Filter & cleaned/oiled it a month back, maybe i added too much oil

 

So it turned out to be a P0446-A, an Evaporative Emission Control System Vent Control Circuit Malfunction... sounds scary but we put some dielectric greaseon the gas cap seal, cleared the code & so far [:-]all is well. I heard the computer will save the code for 80 cycles (a cycle is 20 mins. of run time or reaching operating temp.) so we'll see.
AlsoI did found outI need a new idler arm ... yee haw lol