I have an 04 with a newly rebuilt engine. Got the tighten gas cap on the cel then the check engine light came on. I have replaced the gas cap, the canister and valve under the truck by the spare and the valve on the engine. It would go out and then come back on. Replaced the fuel tank sensor and reset the coedes. went thru an entire tank of gas no light. #/4 of the way thru the second tank of gas and on comes the tighten gas cap and then the check engine light. I'm lost and don't know where to go from here. Any ideas would be greatly appreciated.