P0499 - Where's the EVAP solenoid?

[Brake_L8]

Wow, tons of great info here - thank you all so much. I figured out my problem and you'll collectively roll eyes at what caused it - BUT if I have to diagnose later down the road, this thread will be a great resource to save.

I use this truck to tow with. When I took it to Road Atlanta in early December, my trailer had some wiring that was grounding out against the frame and blowing the truck's fuse for the trailer running lights. I blew through a few spare fuses as I was diagnosing that wiring and ran out of legit spares... so I thought it was so kind of GM to leave fuses in the box for options my truck doesn't have.

The first two fuses I pulled to use on that circuit were for L/HID and R/HID as the Denalis don't have HID headlights.

The third and final fuse? 4WS, because the Denali never got 4 Wheel Steering/Quadrasteer.

Well, SLCHOE's post about wiring got me thinking - this evap stuff has to be on a fused circuit, which one is it? Fifteen seconds on Google got me the answer.

I guess someone at GM decided that the evap system and Quadrasteer could share a circuit, and that it was smarter to label the circuit with the rare option vs. the standard emissions system.

So... I'll be putting a new 15A fuse in the 4WS spot tomorrow and that ought to, you know, let the evap solenoid do it's thing.

 

[ccapehartusarmyINF.(ret)]

quadrasteer how does that work out yah i remember that feature awhile back i always thought id come in handy towing a travel trailer but i had my doubts about reliability
also isnt a quadrasteer axle wider then the standerd axle i noticed on thee trucks awhile back they kinda these extra wide rear fender wells that looked funny

 

[Brake_L8]

quadrasteer how does that work out yah i remember that feature awhile back i always thought id come in handy towing a travel trailer but i had my doubts about reliability
also isnt a quadrasteer axle wider then the standerd axle i noticed on thee trucks awhile back they kinda these extra wide rear fender wells that looked funny

I don't have Quadrasteer - it never came on the Yukon Denali. Only was offered on the Sierra C3, Sierra Denali (03), Silverados and a few Suburbans/Yukons. But, I wanted a truck with Quadrasteer so did some reading on it.

Yes, the rear axle is wider which is why you see the rear fender flares. I think it's 8" wider in total. The steering setup is simple enough but a lot of parts are NLA if anything breaks. There is a "tow" mode that allegedly uses all four wheels but is tuned for better stability when towing.