SQL query problem

Hello,
I'm in the middle of the migration process from MySQL to PostgreSQL and
I cannot understand why this query isn't working (in MySQL it's working
fine). PG returns: ERROR: Relation "_con" does not exist

This is my query:

SELECT
_CON.con_id,
_MOD.mod_ty,
_VER.version,
_YEA.year,
_CON.dri_id,
_CON.man_cod,
_ENG.eng_pow
FROM
db_data.mda_mod _MOD,
db_data.mda_mod_con _CON,
db_data.mda_mak_eng _ENG,
db_data.set_mda_fue _FUE
LEFT JOIN db_data.mda_mod_ver _VER ON _VER.ver_id = _CON.ver_id
LEFT JOIN db_data.mda_mod_yea _YEA ON _YEA.yea_id = _CON.yea_id
WHERE
_MOD.mod_id = '283' AND
_CON.mod_id = _MOD.mod_id AND
_CON.psd <= NOW() AND
_CON.ped > NOW() AND
_ENG.eng_id = _CON.eng_id AND
_ENG.eng_fue = _FUE.fue_id

I will be appreciated for you help.

ML