Service engine soon light on--do-it-yourself or better off at shop?

1999 gmc yukon 38k I'm wondering if this is pre-programmed thing like chrysler is famous for or do I have a problem? seems to run fine--mileage is normal--any suggestions?
I was thinking about buying one of those hand held computers from local store and attempting fix myself--although I may be just wasting my time and $$
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without knowing why it's on, we're kinda shooting in the dark here
Have it scanned and tell us what codes were stored

$$
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after driving a few places today--the light is now off!! what the #%!$# I thought that once that light was on that it stayed on until problem fixed and light reset
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I had a 98 Chev. 5.7 and it did the exact same thing. One of the secondary o2 sensor heating element was beginning to go south.
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Not necessarily, if it finds a issue it will flash until it is taken care of... The problem may be intermediate so it will come and go. I would still get it scanned the code will still be in the computer and now you have a little time to get it fixed or figure out how to do it yourself before it comes a major problem.
mark
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lights that come on and go off are usually, but not always, O2-sensor related

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(top post) When you start your truck the pcm scannd the sensors to check for an error...When it finds one the light will come on...On some sensors when the PCM doesnt detect a fault within a number of start ups if will turn out the light thus letting you know it is not detecting a fault.....But the code will be stored in its memory....It may be nothing but for $20.00 most places around here i dont know about where your at ...Will scan for codes....Intermitted or not ...Ca really say for sure if its gonna be a problem unless we have a code...
Steve C Re: Service engine soon light on--do-it-yourself or better off at shop? Group: alt.autos.4x4.chevy-trucks Date: Sun, Dec 14, 2003, 3:07am (CST+6) From: snipped-for-privacy@mchsi.com (GaryGlaenzer) lights that come on and go off are usually, but not always, O2-sensor related
after driving a few places today--the light is now off!! what the #%!$# I thought that once that light was on that it stayed on until problem fixed and light reset Not necessarily, if it finds a issue it will flash until it is taken care of... The problem may be intermediate so it will come and go. I would still get it scanned the code will still be in the computer and now you have a little time to get it fixed or figure out how to do it yourself before it comes a major problem. mark
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oh, yeah........................
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What were the conditions when the light came on?? Towing, climbing a hill??? Misfires are also a common cause.... Light flashes during the misfire condition and goes solid to let you know there was an error recorded. The light will go off after a certain number of key cycles or trip cycles. It's in your owners manual which also suggests poor fuel or a change in fuel grade. I had similar issues and discovered the valve guides were sticking and spent $1300.00 for a head job. This seems to have fixed the problem as I have a ton more power climbing hills and towing.
Bomber

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$$
As far as I know GM does not flash the light at maintenance intervals. Go to a national auto or similar parts store they generally will let you borrow a scanner or will do it for you. Sometimes it is something that easy to fix, sometimes not...
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