what can cause the evap system to fail on board test
2 Answers
Gas cap, cracked vapor line, flooded vapor canister, fuel tank vapor check valve. You may need a shop to do a smoke test on the system.
Some EVAP system leaks are so small they can't be seen with the naked eye. This is why a smoke test must be done to find the leak. An engine vacuum leak can also trigger an EVAP system code. I just ran into that with one of my vehicles. Hope that helps! Jim