Washer-dryer combo displays E91 and may not start; communication between boards is lost.

Safety first: Unplug the appliance before accessing any control boards.

• Locate boards: Identify the main control board (usually under the top panel) and the motor control or interface board (often near the motor or behind the front panel).
• Inspect harness: Follow the multi-wire communication harness between the boards. Check for pinched, cut, or burned sections and repair or replace as needed.
• Reseat connectors: Disconnect and reconnect the harness plugs at both boards, ensuring they are fully seated and locked.
• Check for corrosion: Look for moisture or corrosion on connectors. Clean lightly with contact cleaner if minor; replace harness if severe.
• Board substitution: If wiring is intact and E91 persists, one of the boards is likely defective. Typically, the GE motor control board is replaced first, followed by the main control if needed.