HP LaserJet Pro 400 color Printer M451 series - Manual (Page 165)

Recommended action
Load the correct paper into the tray, or press the OK button to use paper in a different tray.
Load tray 1 plain <SIZE> Cleaning Mode [OK] to start
Description
The product is ready to process the cleaning operation.
Recommended action
Load Tray 1 with plain paper in the size indicated, and then press the OK button.
Load tray <X> Press [OK] for available media
Description
The tray is empty.
Recommended action
Load paper into the tray to continue printing. Press the OK button to select a different tray.
Load tray 1 <TYPE> <SIZE>
Description
No trays are configured for the paper type and size that the print job is requesting.
Recommended action
Load the correct paper into Tray 1, or press OK to use paper in a different tray.
Magenta cartridge low
Description
The print cartridge is nearing the end of its useful life.
Recommended action
Printing can continue, but consider having a replacement supply on hand.
Magenta in wrong position
Description
The print cartridge is installed in the incorrect slot.
Recommended action
Make sure that each print cartridge is installed in the correct slot. From front to back, the print
cartridges are installed in this order: black, cyan, magenta, and yellow.
ENWW Interpret control panel messages 147