How do you reset the maintenance light on 1991 Jeep Wrangler 4.0L?

You must use the DRB II connector and a computer that has EMR reset capabilities. the connector is close to the master cylinder. good luck.

The 1991 Wrangler may be reset by removing the POSITIVE connection from the battery and grounding it to the negative connection or disconnecting the POSITIVE terminal for 30 minutes. (either way will drain the capicitors in the electrical system)