Service Engine Light

1997 Z71 350 engine. My SEL comes on after starting and sitting at an idle for about 30 seconds. It will also come on when the engine is warm during idle (again it will take about 30 seconds of idle). As soon as I put it in gear and go the light will then go out in all cases. The truck seems to run fine, no noticeable degradation in gas mileage or acceleration. This all started after I had an oil change done on the truck. It is not the gas cap as I have checked that. The air filter has been replaced. Any ideas?

Have it scanned for codes, it could be a lot of things

If you go to an Auto Zone or an O'Reilly's, you can 'rent' (no charge) a reader for OBD I or OBD II, I can't recall what your '97 has in it.

If you can pull a code from your truck, it will tell you what it is. You may not be able to get a code from it, unless it stays on though, but it's worth a try.

my :2cents:

-slacker

Sounds like the O2 sensor.

Sounds like the O2 sensor.

Dude, never replace parts until you have done some diagnosis to determine the root cause of the problem.
If the SES light has come on, the PCM has stored a code that will aid in diagnosis.
Some of your chain auto parts stores have code readers and will scan the PCM for codes for free.
Next, get a manual and follow the trouble chart to determine the cause of the failure.
A little time spent diagnosing the complaint will save you a bunch of money and headaches.