How can I reset the check engine light on a 1996 XJS

Using a scan tool should turn lite out

Reset the check engine light by disconecting the negative battery cable for a minute or two then reconect, be aware that that will not fix any problems that have been present prior to this procedure. After running the car for a while the light usually comes back on, check for a code with a code reader and repair the problem to cause the light to stay out.

Remove the ground for a few minutes or remove the ecu fuse located under the hood fuse box it mark 17amp