P0128 probably indicates a defective temperature sending unit. The
gauge on your dash may still work normally, as there are usually two
temp senders.

P0326 is a little more difficult. It is a generic OBD-II code as
indicated by the zero preceding the actual code. The knock sensor could
be defective, but if I were you I'd fix the temp sender first and then
disconnect the battery to reset the computer. See if this one comes
back.

P1500 is related to the VSS(vehicle speed sensor). Does your
speedometer work? If not, this is why. The sending unit is probably bad
and/or unplugged.

Chris