1999 GEO TRACKER - CHECK ENGINE SOON LIGHT

Don't panic!! LOL Just take the vehicle to an autoparts store and have them use a scan tool to retrieve any fault code(s) stored in the computer. Most parts stores will do the scan at no charge. The code or codes will help note any problems or potential problems that the computer has identified. Sure hope this helped and best wishes.

Mine does that sometimes too. My brother-in-law is a mechanic and he said that pressure in the gas tank can cause that because there is a sensor for it. I just take off the gas cap and let off the pressure and put it back on. The light goes out. It does it more in the summer. Weird, I know, but try it before you spend a bunch of money.

Crappy gas. Try not to get gas while the gas truck is fulling the underground tanks. the trash goes right to the pump you're pumping from. To hopefully solve your problem, disconnect the positive side of your battery for about 10 minutes to reset the computer. If there is no light when you reconnect it, you're good to go. if the light is still on, see if your air filter is dirty. Check your oil. An engine can blow out for lack of fluid? Check your transmission fluid, also. To do this, turn your Tracker on and let it warm up. Hold the brakes while sliding the shifter through all of the positions. Do this twice this check the tranmission dipstick while the car is still running. If it's low add more through the same tube.
If there is no true issue the battery disconnect will solve the problem. Let me know how it turns out.

GO TO AZ, PULL THE DTC CODES,
look them up , learn how to read simple fail codes.

like gas cap loose.
or misfire , very bad P0300
bad egr, p0400

these codes P0XXX ARE A STANDARD. NO SECRET.