To re

Open the printer lid.
Unplug the power cord from the back of the printer.
Remove the upper (OUT) paper tray.
Slide the carriage assembly, which holds the ink cartridges, away from the left side of the printer. If the carriage assembly moves away from the left side, go to step 6.

OR
If the carriage assembly is stuck on the left side, go to the next step.

If the carriage assembly is stuck at the left side, push down on the large black bar directly above the three large rollers and release it so it springs back up. Gently lift the carriage assembly and try moving it to the right again.
Locate the metal gear assembly at the left side of the printer. Directly above the metal gear is the clutch actuator (also known as the slider arm), a small plastic arm approximately 50 mm (2 inches) in length. On the right edge of the clutch actuator is an "arrow" or "tooth" that points down. The arrow on the clutch actuator should be in the space to the right of the metal gear and plastic half-gear just below the clutch actuator.
If the arrow on the clutch actuator is stuck between the metal gear and plastic half-gear, (see Figure 1) lift the clutch actuator and move the arrow to the right of the plastic half-gear. Once the arrow on the clutch actuator is to the right of the gears (see Figure 2), the clutch actuator should move freely right and left about 12.7 mm (0.5 inches).

Figure 1: View of an incorrectly placed actuator arm

Figure 2: View of a correctly placed actuator arm

Replace the upper (OUT) paper tray.
Close the printer lid.
Plug in the power cord to the back of the printer.
Turn the printer on.
Print a self-test by pressing and holding the Resume button (upper button) for five seconds and releasing it.
If the same problem still exists, verify that both ink cartridges are snapped into the carriage tightly and are not loose. See the printer User's Guide or the HP Toolbox in Windows for instructions on installing the ink cartridges.
Try printing a self-test again.
If the same problem still exists, see the Additional Information section below

Carriage stalls caused by the clutch actuator being out of position can result from:

Clearing paper jams by pulling the paper out of the printer without first turning the printer off.
Improper ink cartridge installation, causing the cartridge to bump the clutch actuator and push it out of position.

To prevent this problem from occurring in the future:

Always turn off the printer before trying to clear a paper jam. See the printer's User's Guide or the HP Toolbox in Windows for instructions on clearing paper jams.
Ensure the ink cartridges are installed correctly. See the printer User's Guide or the HP Toolbox in Windows for instructions on installing the ink cartridges