Check transmission light keeps turning on

So when the light comes on, it does not go very fast, right? It sounds like the computer is putting the car into what is called "limp mode." That mode is meant to prevent further problems from developing and yet allow you to drive it to a mechanic.

The service engine light is telling you that the computer has trouble code(s) stored. These codes point in the general direction of what's wrong. They are a starting point, at least. On a 1994 car, as long as it is OBD1 system (which it should be), you can retrieve the trouble codes using a piece of wire, or a paper clip. Here is a how-to guide: https://www.2carpros.com/articles/odb1-isuzu-1985-1994-cars-and-trucks-code-retrieval-procedure-and-definition

The A+B connectors pins are the two on the top row, right side. If it is OBD1, then the connector will be rectangular shaped. If it is OBD2, then it will be more of a trapezoid, and you will have to get it scanned with a OBD2 scanner. The local AutoZone, Advance Auto, or O'reilly Auto Parts can scan it for free.