Paranoid about no CEL

[westtexastiger]

This might seem a little odd for some of y'all. For several months now, my CEL has been on. The car ran fine, no issues with drivability, performance, gas mileage, etc. I got the ECM scanned about 2 months ago, and it spit out code 0440.

I researched on the club's site, and found out it's usually a gas cap, or perhaps another minor inefficiency in the emissions system. So, I replaced the gas cap, and disconnected the battery, twice, to clear the code. The stupid light still came back on. So I just left it, since it wasn't really doing much, if anything, to the car.

Then, last night, as I was driving home and marvelling at how my car JUST NOW turned 60k miles, I noticed the CEL wasn't on anymore. When I parked, I turned the car off, and back on, to see if it was just a fluke. The CEL still didn't come back on. I don't think the bulb burned out, because the CEL light flashed, like all the rest of the warning lights, when I turned the key to "On". When I restarted the car again, the CEL still didn't come on.

Am I just being overly concerned? Can the problem fix itself eventually, or do I need to look into something?

Thanks for the help.

[Blackhawk]

Engine codes are stored for something like 30 turns to the "on" setting on the ignition, once you're past that and the code hasn't reoccurred, then it will turn off. I'm guessing you didn't clear the codes when you scanned it?

[westtexastiger]

Correct. I did not clear them. Does the ECM eventually clear the codes itself? It's been way more than 30 cycles to the "on" position.

[KhellendrosXS]

I think after 100 cycles the PCM will clear out codes that have been there for that long. The other way to clear them is to unplug the negative cable for 15 minutes.

[westtexastiger]

The other way to clear them is to unplug the negative cable for 15 minutes.

I did something similar to that, back when I first noticed the CEL. I think I left the negative battery cable disconnected for like 2 hours. The code came back, though, but I guess the problem slowly fixed itself, and the CEL turned off?

[KhellendrosXS]

I did something similar to that, back when I first noticed the CEL. I think I left the negative battery cable disconnected for like 2 hours. The code came back, though, but I guess the problem slowly fixed itself, and the CEL turned off?

Probably not, see when you reset the computer and the codes if you CEL comes back on it is because

A) The procedure was not done properly
or
B) The problem still exists/new problem has arisen and therefore the CEL is back on again

The PCM does not care if you do fix the issue because it will store all codes for so many cycles until either you clear them or the computer deletes them. If the code came back as you say then the problem was likely not taken care of. As much as I wish they did a car like this cannot 'slowly fix itself'. The light is on, then turns off after X ignition cycles and is finally deleted after another set number of cycles. If the problem persists the light will remain on, if it is fixed it will shut off but still be stored.

[westtexastiger]

So, if I'm understanding you correctly, the last time I fixed the problem, when I did NOT disconnect the negative battery cable to clear the code, I may have solved the problem, but the CEL stayed on for a certain number of cycles, then went off? Would I check to see if the code is actually deleted by getting the ECM scanned again?

[KhellendrosXS]

I believe so, yes. I would have your car scanned and see if a new code is there or if the old one is stored. You should know within a few cycles if your repairs were on the spot because the car will throw another SES light if something is wrong.

[westtexastiger]

It would just piss me off if all it really was was that I hadn't tightened the gas cap right, and finally somehow managed to do it.

[KhellendrosXS]

I usually tighten mine two clicks so it doesnt get super tight but still isnt allowing any leaks.

[westtexastiger]

In my research, I read somewhere to do three, but you're right, it's a PAIN to get off at that many.