the heated O2 sensor is supposed to allow your car to go into closed loop sooner and be more tolerant of leaded racing fuel.
the most likely cause of the code 13 is one of the following:
1) a faulty ECM
2) poor connection
3) bad sensor
given the above, if the ECM wasn't a problem before, it's probably not a problem now. and if the sensor is new, it's not very likely that it's the problem (it's possible but not probable).
check all your connections and check to see if the car go into closed loop or not.
bw jones
