Microwave beeps and displays E1 shortly after pressing START; cooking does not begin.

Safety first: Unplug the microwave from the wall outlet before removing any panels. Microwaves contain high-voltage components that can retain charge; do not touch internal high-voltage parts (capacitor, magnetron area) unless you are trained.

• Power reset: Unplug the unit for 5–10 minutes, then plug back in and test. Sometimes a control board glitch can trigger E1.
• Check for stuck keys: With power disconnected, gently press each button on the keypad. If any key feels stuck or does not click, clean around it with a slightly damp cloth (no liquid into the panel). Dry thoroughly and test again.
• Inspect keypad ribbon cable: Remove the control panel assembly (usually by taking off the top grille and one or two mounting screws). Carefully pull the keypad ribbon cable from the control board, inspect for corrosion or damage, then reinsert firmly. Reassemble and test.
• If E1 persists: The membrane keypad or the main control board is likely faulty. On many Oster countertop microwaves, the keypad is integrated with the control panel. Replacement of the control panel/keypad assembly or main PCB is typically required and is best done by a qualified technician due to high-voltage risks.