SERVICE ENGINE SOON light

Could be carbon in your EGR, but run the codes on it and that will direct you.

sounds like you need to find a good independant garage

The 97 GMCs have a good scanner setup. Go to the nearest Car parts store like Auto Zone, and they will scan it for free. What usually goes wrong at that mileage is the O2 sensors go bad. There are up to 4 of them on that year depending on whether you have a Vortec engine or not. If it is a Vortec, it will say it on the engine plastic cover in the center top of the engine. Vortecs have a dual exhaust setup, with 2 catalytic converters. They have 4 oxygen sensors, 2 before the two converters, and 2 after. The after ones are heated electrically to respond faster when cold. The heating coils burn out, and it sets a code. You won't be able to tell any difference when it is running. The rear O2 sensors are just a check on how the emissions are working. The sensors are mounted on top of the exhaust pipe, and a bit of a pain to do, but not too bad as long as the pipes are cold. They cost about $49 at a discount house, so check around before you buy. The dealer will rip you about $200. I had to use a box end wrench with a dead blow plastic hammer to get mine off. They go back in easy with some anti seize compound on the threads, only don't get any on the sensor itself. Be careful of the wire routing so it is in the original clips, and don't break them.

With the weather being cool, is this something I can put off until spring? Engine seems to be running just fine at present.

Not true, while you can use a scanner to read and reset code. It will clear itself from memeory after about 50 start and runs and the light will go out too as soon as it is repaired and there is no new error code being set. The light comes one when a code is set during a run cycle not because of a past fault recorded in its memory A new fault has to be detected to cause it to light come on even if it is a repeat of a past one, it is still considered new if it is redetected during a run cycle.

As far as changing the O2 sensors, warm the truck up a little bit first, not enough so you burn yourself but just a min or two. I couldn't get my sensor out for anything, was at the point where it was getting ready to round off. Fired the truck up for a min or so and was able to get it out a lot easier, just need that exhaust to expand a little for you.

Hi, I have a 1999 chevy tahoe with the same situataion. the engine seems to run fine but the service engine light soon came on out of the blue. This Truck has 97,500 mi. on it.

Are the o2 sencors a fairly common problem?

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======= ======= Shep, why can't he put it off till spring? Why does he "really need to know the code"?

Just Curious.

And.....I disagree. If the OP's statements are all FACT....then put er off till spring if you want.

~:~ MarshMonster ~:~

======= ======= My advice is to pull the negative battery cable off for about

or......

worry about it.

~:~ MarshMonster ~please post $39 to my paypal acct. for initial diagnosis......... follow ups will be charged at $79 p/hr~

Thanks a lot for the advice guys. As it turned out, following my out of town trip where the light came on, after setting home for the weekend, I started it up and the light was out. If it comes back on, I'll be getting right after it but again, thanks very much...

As I thought about letting it go until the weather gets better, I thought better of that just in case that might somehow control the burn but anyway... Thanks for all the replies.