The Technical Definition: The vehicle's communication network (CAN bus) has lost its connection with the Powertrain Control Module (PCM), which is the main engine computer.

Common Symptoms: This usually causes a complete no-start condition, engine stalling, and a dashboard lit up like a "Christmas tree" with multiple warning lights.

Typical Fix: A weak or dead battery (or auxiliary battery) is a primary cause of communication faults. Beyond replacing the batteries, this code on a Wrangler often points to a faulty CAN bus junction block (STAR connector) located behind the glovebox, or damaged wiring.