Does CEL Goes Away By Itself?

[gabkwong]

I had a CEL (code P0421) this Sun. After driven a couple of days for about 100 miles. This morning it went away when I start the car. I am under the impression that the CEL has to cleared and does not go away by itself?!

Gab

[sammm]

If the computer detects 'normal' readings after a number of 'drive cycles', CEL codes can clear themselves.

It seems CA cars have P0421 issues -
http://www.miataforum.com/vb/printth...6&page=1&pp=25

[gabkwong]

Sammm, Thanks! This make me feel better knowing it is not the CEL light burned out! May be my 1st CAT is getting weak and on life support. I just replaced the 1st O2 sensor, therefor, it can't be the O2 sensor. The P0421 code is pretty specific for the 1st CAT. The O2 sensor had a different code. Can't wait to convert it to run on only one CAT.

[Treibenschnell]

I just put a piece of black electrical tape over it... goes away every time!

[gabkwong]

I just put a piece of black electrical tape over it... goes away every time!

Actually if you ignore it long enough the CEL will eventually burn out and you have a "permanent fix" of ALL your CEL problems!

[POS Racing]

Actually if you ignore it long enough the CEL will eventually burn out and you have a "permanent fix" of ALL your CEL problems!

Yep, just up to the moment the inspector plugs in the CEL reader to your car, then it all comes back again.

[trickyrix]

Yep, just up to the moment the inspector plugs in the CEL reader to your car, then it all comes back again.

...unless you know the right inspector...

[Treibenschnell]

...unless you know the right inspector...

Or don't have a CEL outlet!

[channelmaniac]

I wonder how many years one would get in the custody of the state if one created... err... um... a "test rig to test inspection machines" that looked just like the OBD-II port and allowed the car to pass.

[Titus]

I wonder how many years one would get in the custody of the state if one created... err... um... a "test rig to test inspection machines" that looked just like the OBD-II port and allowed the car to pass.

Now if we just knew someone with hardware and software experience... perhaps someone so in to little projects like this that he or she had there own professional solder station. Hmmm. Who do we know like that?

[channelmaniac]

I know a guy that can do the hardware... he doesn't have programming knowledge though...

[VFR750]

P0421 is a very common code in Miatas and others........my 99 Miata set that code real regular, a new 02 sensor cut the frequencyand since the new spark plug wires its only come back once. I have a scanner so I would just clear it every time, what used to be 2 or 3 times a week is now maybe once every month or two.

[Radio-Active]

Actually if you ignore it long enough the CEL will eventually burn out and you have a "permanent fix" of ALL your CEL problems!

I don't think the car will last that long. I put 50,000 miles on a car with the CEL staying on. Never did burn out.