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did you check what trouble codes were or are set? were the codes cleared after the cap was replaced?
Autozone said the EVAP system code came up, but that those parts dont go bad. Front end of car was slightly damaged when problem started. What is that gadget under the front bumper cover on the drivers side. (It doesn't look damaged.)
I disconnect the battery, the light goes out. Stays out until I have to buy gas and take cap off, or just take cap off. Brand new cap.
getting the exact code really helps in diagnosis. The evaporative system has 3 common failures. The gas cap, vent valve solenoid and the purge solenoid. There is a chance of a leak also, that would need to be diagnosed with a smoke machine. Most modern shops have scanners that can check the vent and purge solenoids by watching the Fuel Tank pressure sensor and commanding the vent closed and the purge open. The evap system is not under the front bumper, by the fuel tank and under the hood. When you disconnect the battery the code clears until the PCM dries to run a evap system test. If you have a leak or one of the solenoids do not work it will set a code. You can either get the car tested or guess vent solenoid or purge and hope there is no system leak.