EVAP vent valve?

Yep, you have the right idea, it sound like a ground issue because when you put power to the valve it doe not open, here is the wiring diagram for the valve so you can see how it works. I assume you have the 2.4 liter correct? This guide can help you check the wiring

https://www.2carpros.com/articles/how-to-check-wiring

Check out the images (below). Please let us know what happens.

Had a vent valve stuck open when testing so I bought a new one.tested the new one and worked good on bench. Tested for12 volts across connector in back of truck with key in and was good. Connected new valve and cycled key on and off and no click.Fabricated a 12volt tail light to test under load and when touching connector would not light up. Just had this surfacs 12 volts with nothing connected. What should I do next. I thought about running a wire from the battery negative terminal to the back with a known good ground and try touching the other lead to the positive side of the connector and see if it lights which would tell me maybe they negative side had an issue. What do you think. Also can't find a good schematic of thd wiring going back to fuse box or PCM. What do you think the issue could be. Thanks
Robert Walbroehl

That sounds like it is operating normally. The vent valve is normally open with no voltage to the solenoid, it closes only when the EVAP system is being tested. The system says "Time for a test", at that point it checks the fuel level, it cannot be under a quarter or over three quarters of a tank. It then closes the vent valve by applying voltage to the valve, and opens the purge valve up front. That applies vacuum to the fuel system. The PCM then counts how long it takes for the vacuum in the tank to reach a certain value within a set time, if the time falls withing the numbers the PCM table has the EVAP purge test worked. It then closes the purge valve and opens the vent valve and times how long it takes for the system to reach atmospheric pressure. It compares that time to another table and if it's good, you don't get any EVAP codes. So looking for voltage by turning on the key won't work because it won't be there. Now if you have a scan tool that can actuate the EVAP valves you can test them for operation. The GM design is a good design but poorly executed. Those vent valves are a failure across the board up to current model years.

Thank you for the information

You are welcome.

Thank you for the info