1995 Chevy Astro dash and tail lights

There is a short in the brown wire to the running lights. You must find where the wire is rubbing ground, most likely causes are near the marker lights them selves, look where the bulb sockets are and look to see if you can see some bare wire. Its process of elimination, you must find the shorted wire, also look under the drivers carpet area this is where the harness goes to the rear of truck, also check for a shorted trailer light harness.