As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE TAXIING TO POSITION ON THE RUNWAY FOR TAKEOFF THE LT FIRE WARNING ILLUMINATED AS POWER WAS ADDED, LIGHT EXTINGUISHED WHEN POWER WAS REDUCED. FOUND 3 CRACKED EXHAUST PIPES, 2 OF WHICH HAD BROKEN OFF OF THE CYLINDERS NR 4 AND 5. FIREWALL WAS INSPECTED SERVICEABLE, PIPES WERE REPLACED.