For two and three printhead printers, the carriage motor contains a position sensor (tachometer) that monitors the rotational position of a circular timing fence attached to the motor shaft. For a four printhead printer, a tachometer positioned along the carriage path directly monitors carriage position from a linear timing fence attached to the bottom of the carriage. In either case, the tachometer detects carriage position, direction, and motion. Also, the carriage motor circuitry has an overcurrent sensor to detect a motor failure (short).

1. Check the motor pulley, drive belt, motor cabling, and tachometer cabling.
   
   
2. With printer power turned OFF, position the head carriage away from the left margin. Turn the printer ON. In the startup sequence, the head carriage should move to the left margin. If the motor fails to move, replace the carriage motor assembly.
   
   
3. If failure continues, replace the motor driver board.

If no error message is displayed, yet the carriage fails to home, check for paper feed operations. If the paper feeds, the problem is most likely related to the carriage motor or cabling. If paper feed fails, the problem is most likely in the power supply area. Refer to Power Supply Check, "Problem:  Printhead carriage fails to home at power ON."