My Brother SE-270D shows error F04 in screen

SOURCE: Instrucitnos for Brother SE-270D Timing Problem

This is not really something you can do yourself (been there, tried that!). The machine has to be almost completely disassembled to get to the timing mechanism. Trust me, it's worth the 30.00 to have it timed.
I think http://www.allbrands.com has a generic timing explaination for sewing machines (use the drop in bobbin one)...I found it easy to follow...but once I realized I had to unplug all the components for the computerized functions... I took it in to the dealer. If you contact Brother & your machine is under warranty, they will pay for the repair (they paid for my first two re-timings). Now I know you HAVE to use BOBBIN thread that is 60 WT only in the bobbin. You will continue to have problems if you don't. Also, this machine uses the class 15 bobbin, but make sure its model number SA156A, which is a hair taller than the SA156 bobbin..both are class 15, but the tiny difference is very important.

SOURCE: Error message on Brother SE-270D sewing machine

The safety device will activate if the machine has a bind or is unable to run at correct speed. If you turn the handwheel is it tight/hard to turn? if it is than thats it. Now what is binding the machine has to be diagnosed.

SOURCE: I have a Brother SE-270D. The top thread is not

A bent needle will cause this. Otherwise the shuttle is out of time, have it serviced..

Testimonial: "Thank you! That is exactly what I ended up having done."

SOURCE: brother embroidery machine broken

Mine was doing the same thing, it wasn't threading right. The thing that pulls the thread down to the needle was out of place, and it wasn't wrapping the thread around the tension. Hope this helps!

SOURCE: "Lower presser foot" error on SE 270D

This happened to me and I eventually realized that there is a small door flap at the top near the "4" in the threading series that can get stuck open. Normally this flap goes up and down with the presser foot, but if it gets stuck open even when the presser foot is down, tapping it or closing it manually will make the error go away.