My check engine light is on. The codes are:

PO134 O2 Sensor Ckt No Activity (Bank One Sensor One)
PO400 EGR Flow Malfunction
PO441 Evap Emission Control System Purge Flow Fault

Any suggestions as to what I now need to fix would be appreciated. Cleared the codes and the Check Engine Light was off for a few hours but it came back on. If the O2 sensor needs to be replaced, which one of the four is this code about?

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• 2001 E320