"However, electrical power continued to be supplied by the Auxiliary Power Unit," the company said, giving no further details on the equipment problem.
It said the aircraft landed in Hong Kong "uneventfully" and that all 271 passengers had been transferred to other carriers.
A Hong Kong Airport Authority spokeswoman said the aircraft touched down without incident at about 3:00 am.
The plane had departed from Kuala Lumpur at 11:37 pm (1537 GMT) on Sunday and was scheduled to arrive at Seoul's Incheon airport at 6:50 am, South Korean time.
As a result of the diversion, the return flight MH067 from Incheon to Kuala Lumpur was cancelled and passengers were transferred to other carriers as well as subsequent Malaysia Airlines flights to Kuala Lumpur.
On March 8, Malaysia Airlines Flight 370 disappeared off civilian radar just an hour into its journey to Beijing, sparking an unprecedented international search across huge swathes of the Indian Ocean and South China Sea.
Malaysia has said the plane -- with 239 people aboard -- veered inexplicably off of its intended route in an apparently deliberate act.
Aircraft and ships from several nations have picked up a suspected trail in the southern Indian Ocean, where large pieces of floating debris have been spotted but not yet retrieved to determine if they are from MH370.