Q: check engine light

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Hi, a few months ago a check engine light came on my Hyundai. Firestone ran diagnostic codes and replaced canister purge valve, vent shut valve and intake hose assembly. After about a month check engine light came on again, they ran the codes and replaced my fuel cap. Again the car was fine for a month or so and the light came on again. They ran the codes again and they said i have a faulty fuel tank pressure sensor and replaced that. That was last week and today the light came on again! Before I take it back to the shop I was hoping to figure out of they are just ripping me off by having me replace all these parts or is it really possible that all these parts are failing in such rapid succession? It seems incredible to me that all of these parts need replacing. Is it possible they are misdiagnosing the problem? Is it possible i just have a faulty check engine light sensor? I am also considering buying my own code reader (they are about $15 on Amazon). Is that worth it? Thanks! Leeka
My car has an automatic transmission.

These are all parts related to the fuel tank which indirectly relate to the pressurization of the tank. The canister purge valve is something that allows excess pressure to be removed from the tank. The vent shut valve and intake hose assembly is the actual intake tube that moves the fuel to the tank when you are pumping the fuel into your tank at the pump. As you know the fuel cap maintains pressure when it is sealed correctly. Finally, the fuel tank pressure sensor is a sensor that relays the fuel tank pressure in pounds per square inch (PSI) to the car’s computer. These components all work together to maintain a specific fuel pressure in order to supply the fuel injection system in your car properly. Without sufficient fuel pressure, the intake would not work properly. Although, it is coincidental that each of these parts failed successively, it is not entirely unreasonable as they all work together and respond to each other indirectly. A faulty check engine light sensor is highly unlikely as this is simply a reflection of what the computer reads. Yet, if you would like, a certified technician from YourMechanic can come to your home or office to diagnose your Check Engine Light issue.

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