Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hi there, I am Cam. For your C0281, that is likely a wiring issue at the brake switch, brake light switch itself or possibly even the connections in the back of the left dash fuse block.
For the P0446, that is most certainly a bad EVAP vent valve and likely a plugger evap canister. I would remove the canister on the front of the tank, clean it out. Put low pressure compressed air in the smaller 2 ports while tapping on the hosing, plugging the other small part and blow all the dust out of the large port. The valve is located avocet the frame cross rail that the back fuel tank strap attaches to. Just replace that as its likely full of dirt, not sealing and causing the codes.