It sounds like they are guessing at it and just clearing the code. As I said before this will take about 100 miles to run through the system test to determine if it fails.
If it were me, I would be calling the manager and tell them what is happening.
These are difficult issues to find but they need to find what the fuel tank pressure sensor is doing.
Basically, the way this small leak test works is on every time the engine runs and then shuts off, it checks for a large leak. If the large leak passes, then it continues to check the fuel tank pressure over time while the engine is off.
If there are no leaks, then the ECM expects to see a certain pressure in the fuel tank after a certain amount of time. If this pressure is lower than it expects to see, then the ECM assumes there is a leak in the system.
This means, the purge or vent solenoid could be leaking. The fuel pressure sensor is not accurate. Or the ECM could the issue.
Unfortunately, they only way to know this is to test the system as I am attaching below.
What I suspect is happening is the mechanic that is working on it, doesn't fully understand the system and how it works. Clearly this is based off only what is in this post but from my experience with mechanics, this is a complicated system to understand but once you do, it is pretty simple.
If they already replaced the canister, purge solenoid and the solenoid again, then they have to test the other components as shown below.
Images (Click to enlarge)
Wednesday, October 27th, 2021 AT 8:18 AM