Fixed: Check Engine Light P0442, P0456, P0446

When our vehicles have a Check Engine light showing, I take it to our local AutoZone for a free diagnosis.

In the past, when our 2004 Toyota Corolla had a check engine light it was usually P0442, which was 

likely the fuel tank cap not being closed completely.  However, the fall of 2021, the check engine light started showing P0446 and P0456, which are also small EVAP leaks and possibly could be a leak in the fuel tank cap.  However, I was sure that I had tightened the fuel cap each time.   

At first it was a P0442 code. I took the following steps to address the problem:

• Cleaned fuel tank cap gasket and fuel tank filler pipe.
• Make sure the fuel tank cap clicks when tightened.

After a several fill ups the check engine light went off.

But the check engine light returned.  This time as a P0446, which sounded possibly worse.  Again, I took the same steps:

• Cleaned fuel tank cap gasket and fuel tank filler pipe.
• Make sure the fuel tank cap clicks when tightened.

And the light turned off again after a few fill ups.

But after a few weeks, the check engine light returned as a P0456.   It did not go away after a few fill ups.

I decided to do a cheap DIY repair:  Buy a new Toyota OEM gas cap.  (I read that secondary market gas caps often have leaks that cause a check engine light.)    The cost was only $25.   After several fill ups, the check engine light went off and hasn't come back on.

Saved at least $100 since that was the cost for a mechanic to diagnose the issue.

Disclosure:  No compensation was received for this post.

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This is not financial nor car maintenance advice. Please consult a professional advisor.

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