g_murray

Most code readers "expect" you to perform a 'first time' diagnostic in this sequence:

i) Plug code-reader into OBD-ii port with engine and ignition off. If 'alarm' or 'immobilizer' is on ...turn it OFF!
ii) Look at code reader display. It will probably say something like "do you want this to be a 'fresh' reading?' (i.e. if you diagnosed another car, prior to this diagnosis, then you need to erase the PREVIOUS readings, otherwise you're 'contaminating' THIS reading with OLD/IRRELEVANT data.) Capiche?

*** NOTE - THIS IS NOT CLEARING THE CEL *** ...so it is 'safe' to say YES.

iii) Turn ignition key to ON -- you WANT to see the dials light up ...but DON'T start the engine.
iv) Set the code-reader to 'diagnose' the car - now that it can actually talk to it.
(What the code reader will do is first see what 'protocol' the OBD-ii system is using ...then interface with it ...then do the diagnosis. This may take a minute or two ...so be patient.)
v) The code reader will then, probably, present you with a menu system whereby -via menu option -- you can SEE the code(s) that are stored (both 'live' and 'pending' codes) and give you the option of either leaving them alone OR totally clearing them.

In my experience, because, on our cars, the act of clearing the codes ALSO trashes the 'readiness monitors' (which are a friggin bitch to 'set') -- then you really need to think about totally clearing the CEL (check engine light).

If the CEL is on for something 'minor' (e.g. a misfire) then I would NOT clear the CEL because there's a good chance that the CEL will go OFF BY ITSELF. Why? ...because if the OBD-ii system does NOT detect "that same error" in the next few drive cycles ...then it deems it a 'nuisance error' and turns off the CEL all by itself.

However, if the CEL is on because of something that is clearly a 'big' or 'recurring' problem (e.g. bad O2 sensor, SAI problem) ...then you now have several choices: drive around with the CEL on - knowing that, come state inspection time you're in deep doo-doo or clear the CEL and hope that the problem cures itself (ha!) or that the OBD-ii system doesn't (for whatever reason) detect the problem in the future. But you GOTTA know, in your heart, that you're living on borrowed time.

My $0.02,

Gerry

becker - 97'C4S

Re; Readiness codes , get a reader that reads you those codes. I posted a while ago how I managed to get around that but repost here: This is NoVA anyway, I reset my CEL and went to the test the results were not ready come back later, I knew my CEL will come back on, but just needed to get the readiness code set, I drove it around 100 miles with a few starts and went back to the test, the guy ran it it came out fine.

BTW I think I was right at the edge as when I got there I didn't shut the engine off in fear the CEL will come back on after the guy finish the test I shut it off for paying and al little chat and sure enought after I restarted it came on right there I know the guy and he said we go by what the test computer said :-)

g_murray

Wow! ...by the skin of your chinny-chin-chin !!!

hawk993

Jesus...does anyone do a search anymore? There are only about 1 million threads on CEL

Allen

Uhhh...I'd say that would be a resounding YES. Notice that this thread was originally posted MORE than (2) years ago. So I think "spg993tt" did a search, found this this thread and responded.

Hey...this is my 500th post...kudos to me...