CO-34, known also as "See-Oh Three Four," functioned as a CLL-M2 binary loadlifter and fought for the Resistance during their struggle against the First Order.
Sometime between the years of 31 and 32 ABY, Admiral Ackbar of the Resistance was taken prisoner by the First Order. Fearing his potential execution, the Resistance established a dedicated team focused exclusively on finding Ackbar's whereabouts. This team, under the command of Captain Hoff, eventually captured a First Order droid named O-MR1, believing it possessed knowledge of Ackbar's location. During their return journey to the Resistance base, the team's spacecraft suffered a crash on the planet Taul. Only CO-34, O-MR1, a protocol droid identified as C-3PO, a medical droid known as 2MED2, and a pair of security droids named PZ-99 and VL-44 survived the incident.
Under the leadership of C-3PO, the surviving droids detected a signal originating from a First Order ship. As they proceeded to trace the signal, they encountered an assault by spice spiders. PZ-99 made the ultimate sacrifice, drawing the spiders' attention to himself to allow the others to escape, resulting in his destruction. The remaining droids were soon subjected to another attack, this time by Thidaxx and can-cell. VL-44, 2MED2, and CO-34 were all destroyed during this second engagement.