Gas cap and check engine light

Asked by Jun 10, 2017 at 12:18 AM about the 2017 Ram 1500 Big Horn

Question type: General

I have had a 2017 Dodge Ram 1500 for
a month I bought it brand-new you had
six miles on it today I went to put gas in
my truck and when I did that I noticed
that my gas cap was gone the only way
this could have happened was it
somebody stole it but shortly after that
I noticed my check engine light came
on is there a possibility that that light
came on because my gas cap was
missing I went and bought a new gas
cap and put it on hoping the light would
go off but it did not I've only had this
truck for a month and like I said it only
had 6 miles on it I don't feel like the
light should be on already

2 Answers


Absolutely. Without the gas cap on it will definitely trigger the check engine light. An EVAP system trouble code has set. What you need to do, with the new cap on drive your truck normally and let the gas gauge drop below 1/4 tank. Then fill up. Do the same a second time. The check engine light will go out. The computer will only run the diagnostics for the EVAP system when your gas gauge is between 3/4 and 1/4. So if you're above 3/4 the diagnostics won't run and the light will remain on. Once the gas gauge drops to just below the 3/4 mark the computer will run the diagnostics for the EVAP system. Once the diagnostics runs and passes 3 times, which it will with the new gas cap on, the check engine light will go out and you'll be good to go again. This can take a few days so be patient and drive normally. HTH. -Jim


Yes the light will come on for a missing or loose gas cap, you can go to an autozone type store and have the code cleared and that will turn off the light if that is why it is on. If it comes back on then return to the dealer as you have more than just a gas cap problem.

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