The bucking and surging has not happened again, BUT..... I found out what the P2270 came from.

Turns out "they" are correct about Cheap O2 sensors including Bosch branded ones. They do read about .2 Volts low and the heater apparently does not work!

I put an NGK #2 O2 sensor in yesterday and noticed A) the reading goes up to "normal" 3 minutes faster now, and B) the new "normal" reading is about .740 Volts Vs the cheap .565 Volts.

The cheap #1 sensor seems to be working fine. I don't think the heater is needed for the pre-cat sensor.


Moral of the story: Don't use SG brand or Bosch brand for the #2 (after-cat) O2 sensor.

Thankfully, I get a huge discount at NAPA. $15 for the cheap one, $53 for NGK. By the way; NTK is the official brand name of NGK O2 sensors, don't get confused when ordering both names are on the box.