The machine detects the ink by shining a light through the rib in one edge of the ink cartridge. Apparently yellow is close enough to nothing at all, that the sensors get a little out of whack. Here's how to reset the sensors:
- Get a dinner plate or something to set the ink cartridges on, that won't absorb ink, and is easy to wash.
- Unplug the machine's power.
- Open the machine and remove all four inks, setting them on the plate.
- Close the machine.
- Plug in power.
- The machine will begin it's start-up procedure and complain about the missing inks. It will tell you to replace one specific ink first (black, I think).
- Follow the instructions on the display, installing one ink color at a time. When all four inks are in, it should be OK.
Use Brother inks. They have a little black floater in that rib, and some of the aftermarket inks have had a problem with the floater sticking.
There may be another problem causing this. The ink may really be low, or the sensor board may be off its mounts in the machine. But the routine above is quick & easy, and it fixes the problem more than half the time. You can't run without any of the colors, because that means air bubbles are getting into the ink tubes, and that can lead to dried ink blocking the nozzles.
This is unrelated, but when you peel the sealing tape from the bottom of the ink ctg., do it slowly. Brother has found that sometimes, when you strip the tape off too fast, a little glue remains stuck in the nozzle, blocking it. If that happens, dig the glue out carefully with a pin & it will be fine.