The 1996 is a OBD II diagnostic system and the codes will need to be pulled. Autozone use to do this free.
How do you reset check engine light for the 2009 Chevy trail blazer?
The check engine light is triggered by the Engine Control Module (ECM). The ECM receives information from many sensors and determines when to illuminate the check engine light.
Check for vacuum leaks.
Check the motor mounts.
Random cylinder misfire
Check the engine thermostat. Its probably stuck open.
Bulb may be blown or has been removed.
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
Check for vacuum leak
The transmission fluid on a Chevy Blazer can be checked by idling the engine and allowing it to reach operating temperature. The dip stick can then be removed and checked based on the markings provided.
You fill in the same place you check it at the top left above your engine
At key on it should come on for a couple second "bulb check".