2005 Trailblazer 4.2L I6: Recently purchased this vehicle and had a new fuel pump installed since the fuel gauge was not working. Immediately afterwards, I was getting the P0455 code. Tried the new gas cap, then had them check their connections again, but still getting the code. Rather than start throwing parts on it, I took it elsewhere to have a smoke test done thinking they may have installed/reconnected something improperly. The new shop found that the vent valve was bad, so had it replaced. That lasted a day or two, but now still getting the P0455. Took it back today and they found that the vent valve is getting intermittent power to it and throws the code. They had checked it and found it had power, then all of the sudden it didn't. Any ideas what could be the cause of the intermittent power? They said they could not see anything out of the ordinary that may have happened when the first shop replaced the fuel pump. The vehicle does run well with no other issues.