Nissan Repair: emission test failure, test failure, o2 sensor

Question
My 97 Altima with 160K failed emission and has the dreaded check engine light lit.  Codes that come up are P0325 and P0141.  I changed the O2 sensor on the chance this was the problem - no luck.  Codes indicate knock sensor and  O2 Sensor heater Circuit malfunction.  Looking for a way to pass the test with the cheapest cost.  Thanks.

Answer
Christopher,

Replace the knock sensor and if you replaced the wrong o2 sensor replace the other one.  Before you replace another o2 sensor have the codes cleard and rechecked.  The knock sensor is a must since the engine only runs in limp mode with it out.  Then reset the codes and drive atleast three times before you go in for smog or the computer will rat you out that you just reset it.