check engine reset button

there is a diagnostics hook up port under the hood on the driver side by the air filter housing. You need one of those old scanner machines to erase the codes.

You can run the diagnostic code on yours without a scanner because it is OBD-1

You connect two terminals on the DLC-1 and count the flashes on the dash light.

Even though it seems to be running fine to you, the engine computer has detected a fault and the best idea would be to correct it. The person doing the servicing may have dislodged a wire somewhere - if it came on after their work, they should remedy the condtiion.

If it started after someone worked on it they likely did something wrong.