Check engine light

Hello, I have a Nissan Altima 2000 with about 98,000 miles. The “check engine” light has been on. This happened once before and eventually the light went off, but now it is on again. I read the manual and it said that the gas cap isn’t on tight enough. Checked that and it is fine - but the light never went off. Should I bring it in to a mechanic? Thanks in advance for your help!

Try a local chain auto parts store. They often can read the computer code for free or loan you the tool to read it. Then post the code results here. That’ll save you a $100 mechanic’s fee.

“I read the manual and it said that the gas cap isn’t on tight enough.”

A loose gas cap is just one of–literally–hundreds of possible causes of a CEL lighting up. As Goldwing stated, most auto parts stores will read the stored trouble codes for you–gratis.

When you come back to post the results, be sure to give us the actual code(s), which will look something like “P0123”. Once we see the specific codes, then we can likely give you some specific advice.

Since you stated that “the light has been on”, it is possible–based on how long the light has been on–that there are actually multiple codes and multiple problems. While a steadily illuminated CEL is not an emergency situation, it is still not wise to ignore it for more than a few days.

On the other hand, a blinking/flashing CEL is in the category of an emergency. If the CEL is blinking/flashing, that means “get thee to a mechanic immediately”, before you cause very expensive damage to the engine and/or the catalytic converter. I am hoping for your sake that your CEL has been steadily illuminated, rather than flashing/blinking.

Whenever you get a CEL that posts It will not go away until the CEL is cleared. You can also unhook your battery cables to reset the engine computer…This is the only way to clear it without the handheld scan tool.

The scan tools have gotten so cheap nowadays that there is barely an excuse not to have one…even Walmart has them under $50… AutoZone and P-Boyz will read and clear the codes for you.

The first time you got a CEL and it went off was a minor issue…There are several degrees of severity to the CEL’s The minor ones will post…and illuminate the light and then go off again if the issue corrects itself…IF it is a MINOR CEL… If it is not a minor code then by default when the CEL posts it will not go away until it is cleared intentionally…EVEN IF the issue has resolved itself since the posting… Just how it is designed.

Without a scan tool…I would just disconn the batt terminals for like 5 -10 minutes and then reconn… SHould be gone now… But then again…YOu dont know what the CEL is trying to tell you…but… Oh well…

My feeling is that your manual says that a loose gas cap could be a possibility and that statement in the manual was probably a catch-all generic one that doesnt mean anything.

If your manual flat out said that a CEL means a loose gas cap then the manual needs to be deposited instantly into the circular file.