From your last comments, especially the last one on Hennes' answer, it seems obvious that you are looking for the EXISTS clause, which was what I assumed from the start. So please check, if the following query works for you.
SELECT
count(*) n,
max(pce.insert_ts) last_insert,
pce.p_code,
dpc.m_operation
from tcp_data.fw_p_erg pce
inner join tcp_data.fw_dim_p_code dpc on (pce.p_code = dpc.p_code)
where dpc.show_class = 22
and pce.p_code not in ('42282221')
and not
(
pce.p_code in ('23040400', '23040401', '23040411', '23040412', '23040414', '23040496', '23040497')
and
exists (select * from tcp_data.fw_p_erg xce where xce.tcp_id = pce.tcp_id and xce.p_code = '46262255')
)
and not
(
pce.p_code in ('21041019', '21041015', '21041024')
and
exists (select * from tcp_data.fw_p_erg xce where xce.tcp_id = pce.tcp_id and xce.p_code = '42282241')
)
group by pce.p_code, dpc.m_operation
order by last_insert desc, n desc, p_code
;