BKPF-TCODE is BAPI

Hi,

Can anyone share with me the place where BKPF-TCODE is defaulted to BAPI?

I have checked our GGB1, BADI BADI_ACC_DOCUMENT, BTE and include program LACC9F20, we didn't update BAPI in this field. But we still have doc updated with BAPI tcode.

The document is posted via Z program via BAPI BAPI_ACC_GL_POSTING_POST. We didn't pass the tcode in bapi parameter, by right it should copy the Z tcode. document type is SA, reference txn BKPFF.

Seriously no idea how to trace this tcode update. please help. thanks