The cat converter on my 1999 2.2L Sonoma went to pieces internally: lots of rattling, like broken stuff rolling around in a can. At the same time, a steady "Service Engine Soon" light came on. I got a new OBDII cat installed this a.m. The Service Engine light is still on and I'm wondering how long it will take the ECM to figure out the problem is fixed and turn the light out? I've read anywhere from 4 to 50 starts before it clears itself. I've also read you can clear it by disconnecting the battery but have seen some cautions about doing that. On some cars, apparently, if you clear the codes by disconnecting the battery it will register some sort of "Unready" status on the computer for a certain amount of time and, if you take it in for smog test, it will fail due to that. I've got to smog this truck by 1 March. Is that long enough for it to clear by itself ... or for an "Unready" status to go away if I disconnect the battery? Any advice appreciated.
Service Engine Light - How Long 'Til It Goes Out?
Feb 17, 2007
6 Replies
once the problem is fixed
Have you actually read the codes stored? Or are you just assuming that the cat is only problem?
I haven't read them yet but am going to next week. So, yes, I am assuming ... but my assumption is based on the fact that the cat breaking up and the Service Engine Soon light occurred at (nearly) the exact same time. And I've never had a code stored or a light in the previous 8 years. I guess it could be just a coincidence, but I still strongly suspect that the code will turn out to be a message from the #2 O2 sensor telling me that the cat is no longer doing its thing.
OBDII systems have to have the codes cleared. They don't clear themselves from what I understand.
I have twice had the check engine light come on due to a missfire. In both cases the light went out after the first complete engine heat cycle after the misfire cleared. Although this happened a few years ago I can't help wondering now if the missfire was related to the manifold coolant leak that I just fixed. At the time I assumed it was fuel contamination.
Andy (1990 1500 Express 5.7l)
Sorry about the typos. Just to keep the record straight the vehicle is a 1999 (not 1990) 1500 Express.
Andy
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