Depreciation key issue

Hi experts,

in depreciaon area of AS01(for creation of asset),if i put depreciation key J004 and put useful life like 4",then i save it.But system shows following error:

Asset  INTERN-00001 0       Motor Car (Honda Accord V6)  MH-01-NACoCd. 4000

01 Book depreciation

E651 SYST: Depreciation key J004 is incorrect

Please advise.

Regards,

Samaar