Originally Posted by Bladecutter

I concur.

Make sure you get a new gas cap now, and see if that helps with the trouble codes the shop is getting. Also, the charcoal canister should be inspected to see if it is full of gasoline. If it is, it needs to be replaced.

The way the emissions system works is after the gas cap is sealed, there is a valve in it that opens as a vacuum is created in the gas tank as the fuel is consumed by the engine. Then the vacuum reaches a certain pressure, the check valve opens, letting air in to replace the used gasoline.

The fumes created by evaporating gasoline, however, can not push their way out of the gas tank through the gas cap, and instead expand through a small hose towards the charcoal canister. There is a purge valve there that allows the engine to ingest these fumes under certain conditions, as the valve is controlled by the motor.

Since that hose is directly connected from the intake manifold to the purge solenoid to the charcoal canister to the gas tank, if the computer tells the purge solenoid to stay open, there is direct engine vacuum being applied to the gas tank. If the gas cap stays locked tight, the gas tank could collapse over time.

What I think you are looking at has been a long term failure.
The gas cap failed. The purge solenoid was told to stay open by the computer, and eventually failure.

What you might also have is a damaged hose between the engine, the purge solenoid, the charcoal canister, and the gas tank. They will need to test all of the hoses to see if there is damage done, and replace if needed.

So, replace gas cap, test all hose lines, test solenoid, test computer functionality for solenoid operation.

BC.