Can't pump gas with Code p0449
 

My 08 Suburban threw code P0449. I replaced the Vapor Canister Vent Valve and the code still shows immediately. Dealer says there is some kind of ground short and recommended a new ECM at $725. I don't trust them as they sold me a new PCM for my fuel pump which wasn't the actual problem. That turned out to be a short at a wiring harness, found later.

Any way, I took my truck back and now there is no way to add gas to the tank without the pump immediately clicking off. Took a good 25 minutes the other night to fill the tank. Any way around this? I'm working on finding the short in the system. When I wiggle the wires near the new canister, you can here the solenoid clicking on and off, so I think I am close, I just can't find it.