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Check Engine Light came on while driving

While driving on the freeway my “service engine soon” light came on. The vehicle runs fine, idles fine, starts normally but the light stays on. So what’s the problem? Oxygen sensor? or something else? Vehicle is 2002 GMC Sonoma pickup w/4.3 liter V-6 motor and 72,000 miles.

If it is truly service engine soon you may need an oil change. If it is the check engine light, stop by an auto parts store, frequently (except CA) they will read the codes for free. Post the code here, it will look like Px123

If you don’t have an owners manual, most likely it is available online.

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Service engine soon usually means some preventative maintenance item needs to be performed. This should all be spelled out in the owners manual.

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https://www.shadetreegarage.com/check-engine-light/

Tester

That’s not the way Toyota does it on my Highlander. There’s a Check Engine message and a Service Engine soon message.

Check Engine - ECU error.
Service Engine Soon - Every 5k miles as a reminder to either do an oil change or tire rotation and oil change.

We’re not talking about your Highlander, now are we?

Tester

And the link you provided isn’t for GM now is it?

It’s the same as a CEL, per the owners manual:

"This system is called OBD II (On-Board
Diagnostics-Second Generation) and is intended to assure
that emissions are at acceptable levels for the life of the
vehicle, helping to produce a cleaner environment. The
SERVICE ENGINE SOON [US] or CHECK ENGINE [Canada] light
comes on to indicate that there is a problem and service is
required. "