Brother BES-1262 error

here's the problem; error E-1E and presser foot 2,4,6 remains lowered

what the instruction book says:

This is displayed when every other head control is selected or when the
bed is retreated (including when the power is turned on). Remove the
presser foot of the retreating head and press the return key or turn the F/B
switch of the head to either side. If every other head control is not selected
or the bed is not retreated, the bed sensor position may be faulty. Readjust
it.

• The message, "Is the presser foot
removed?", is displayed on the
machine controller when the power
is turned on.
• The red LED of head 2 or 4 or 6
does not light and the presser foot
remains lowered.
• Is the retract bed sensor adjusted properly?
Adjust the retract bed sensor of the faulty head. (Refer to "Replacing
the retract bed sensor PCB".)
• Refer to the block diagram showing cable connection and check
connection from the retreat bed sensor to the main PCB.
• Check to see if the frame type is set to every other head with the machine controller.

Is there anyone who knows where is the bed sensor and how to adjust it ???

Thanks