Kenmore Dryer Error Code F-40

The F-40 code means the dryer has lost communication between the machine control board and the motor control board. These two boards must exchange signals continuously for the dryer to operate. When that signal is interrupted, the dryer stops running and displays F-40. The fault can be caused by wiring problems or a failed control board.

Unplugging the dryer for a few minutes may temporarily clear the code, but if the underlying communication fault is still present, the F-40 error will return. A reset does not fix a failed board or damaged wiring. It is only a useful step to confirm whether the fault is intermittent or persistent.

Repair costs depend on what component has failed. If only a wiring harness repair is needed, costs are generally lower, typically in the range of $50 to $150 for parts and labor. Replacing a motor control board or machine control board can bring the total to anywhere from $150 to $350 or more, depending on the specific board required and local labor rates.

Some causes of F-40 can be addressed without professional help, such as reseating a loose wiring harness connector. However, diagnosing deeper wiring faults or replacing a control board requires working inside the dryer cabinet with the power disconnected and some comfort with electrical components. The diagnostic process starts with TEST #3b, which helps identify whether the problem is in the wiring or one of the control boards.

No, you should not attempt to operate the dryer while F-40 is active. The dryer has shut down because communication between its control boards has failed, meaning it cannot properly manage the motor. Running the dryer in this condition could lead to further damage to the control boards or the drive motor.