'99 S10-service engine soon light

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take the truck to any auto zone etc. and they will scan it free ..

Agreed, do what Tasty advises. Stop at advance autoparts or autozone. They will scan it for free. Simply disconnecting the battery is dumb because you're trying to rid the symptom and not actually cure the problem. The light comes on for a reason, find out what it is and fix it..

take the truck to any auto zone etc. and they will scan it free ..

10-4 on the free code check but do use caution when getting them.
And leave that battery cable alone.
Just get the code no and post it back and someone will help you

Use Caution when getting the free code checks please.
Some parts places do offer free code checks. And also free repair advice. But beware. Just get the code no and post it back here and someone will help you.
They offer the free code checks in the hope of increasing there parts sales.
Almost all of them will also offer mechanical advice and some know what they are doing.
But just remember most of them are parts people pulling codes for free.
Not trained professional tech/mechanics. Even if they pull a 02-sensor code or another sensor related code it does always mean to replace that sensor and your problem will be fixed.
Please just get the code no and post it back here and we will help you.