FMI 644 CAT Fault Code

Cause :

Malfunction in the thermostat control system. The on-board computer reports problems with communication with the control unit, so a possible cause may be poor contact. The cooling system circuit is open, which may affect the operation of the power unit as a whole.The most common mistake when addressing this code is replacing the starter or PCM when the damage is in the wiring or other components. Thus, it's extremely important to conduct a thorough diagnosis before replacing anything to avoid unnecessary replacements of parts.