Display shows E4 and the air fryer will not start or stops mid-cycle.

Safety first: Unplug the air fryer before inspecting cords or connections.

• Step 1 – Check power source: Ensure the air fryer is plugged directly into a properly grounded wall outlet. Do not use power strips, surge protectors, or extension cords, as they can cause voltage irregularities.
• Step 2 – Try a different outlet: Move the Cosori air fryer to another known-good outlet on a different circuit. Avoid outlets shared with high-load appliances (microwave, toaster oven, etc.).
• Step 3 – Inspect power cord: Examine the Cosori power cord for cuts, kinks, or burn marks. If damaged, the cord set should be replaced; do not tape or splice the cord.
• Step 4 – Internal inspection (advanced): With the unit unplugged, remove the rear or bottom cover to access the AC input terminals and main control PCB. Check for loose spade connectors, burnt components, or swollen capacitors on the board.
• Step 5 – Replace main control PCB: If E4 persists on multiple outlets and no external power issues are found, the internal power supply section of the main control PCB may be faulty. Replace the main control PCB / power board as a complete assembly.
• Electrical safety: If you are not experienced with mains voltage electronics, do not attempt board-level repairs. Contact a qualified technician.