* Bad bulb: Check the left tail light bulbs. If they are burned out, replace them with new bulbs of the same type.
* Bad ground connection: Check the ground connection for the left tail lights. If it is loose or corroded, clean it and tighten it.
* Bad wiring: Check the wiring for the left tail lights. If there are any breaks or shorts in the wiring, repair them.
* Faulty light switch: Check the light switch. If it is faulty, replace it with a new light switch.