This is huge for us! So we have a 2008 Scion xB that has had a nagging problem since we bought it used 4 years ago. Three dashboard lights go off -- Check Engine, VSC, and Trac Off. These three lights are coupled together and can go off for a wide variety of reasons. They go off so frequently in these older Scions that owners call them the "Three Stooges." The car runs beautifully, by the way.
Every time these Stooge lights would go off, we would try to figure out the problem. We'd have the error codes read (various evaporation problem codes) and consult with mechanics. We've had that darned car in the shop three times in the past two years. Each time the mechanics said they looked at it, but were unable to figure it out. The mechanics just advised to keep driving the car and not worry about it.
Last week we had finally had enough, and DH devoted his whole attention to it. He did a deep research dive online, and narrowed the problem down to two suspects: one of the evap valve solenoids, and the vapor canister. He took out the unit with the solenoid, and tested that. Seemed to be ok. He then took out the vapor canister and lo and behold there was a small crack in it! The replacement canister runs about $800. DH did more research and decided to try to fix the existing canister. He got a special sealant that is graded to resist gas and gas fumes, and made the repair. The canister then held a vacuum! He reassembled everything, and lo and behold -- no dash lights. Good bye Three Stooges!!! And thank you internet and Youtube.
This repair (once you diagnose it/know what needs to be done) seems to run about $1400 in a shop. $800 for the part, and ~$600 for labor. Our total cost was $25: $20 for a device to measure vacuums, and $5 for the sealant.
Even if the repaired canister eventually fails, I feel like this whole process was a huge win. We can always buy a replacement part and DH can install it, saving big $. And we learned a lot.