My car just had a tune up i took it to auto zone for a diagnosis and was told something about gas cap my check engine light is still on
My car has 170166 miles.
My car has an automatic transmission.
When the check engine light is on, it means that the ECU has detected a malfunction that will affect emissions. In your case, if the Auto Zone guys suggested that the gas cap was loose, then you may have had a P0440 code. Which might indicate an air leak in the fuel vapor recovery system. The gas cap is the simplest thing that can go wrong, but if that was not a successful fix, then you may have a leak in a vent line somewhere. The most convenient way to deal with this problem is to contact Your Mechanic. They can send a technician to your home or office to check out your Nissan and make a recommendation as to how to fix it.