F5JL‑12A27‑DA is a Ford ignition control module used in heavy‑duty 2.5L and larger industrial engines. Common failures include burned fuse contacts on the input power pins, shorted ground paths, and corrupted firmware causing loss of spark or intermittent operation; visual inspection often reveals cracked PCB traces or swollen electrolytic capacitors. Begin troubleshooting by verifying 12 V supply to pins 1/2 (ignition voltage) and confirming proper grounding, then check the high‑current spark output wires for continuity and correct pin assignment per Ford wiring diagram. Finally review any stored diagnostic codes from the engine control unit for related ignition faults before proceeding with module replacement or reflash.[oss-gpt-20b]