I just put my 396 in 250 miles ago, same o2's i had a year ago. They are bosch sensors. At idle im getting 0.0 and running at steady throttle they are jumping between 0 and .79. Also at idle if it idles for bout 30 seconds the rpms drop and i get a ses code with says both banks are running lean. Plugs are golden brown not white. I know ac delcos are the best im just trying figure this out before i buy 100 bucks worth of senders. Thanks, Glenn

 

I went with bosch also and wasted my money trying to be cheap. I went with ac delco short after and you really do get what you pay for. This has proven true with anything ive put on my car and I just dotn bother with anything other than oem anymore unless its a reputable aftermarket part. A good rule of thumb I like to use for sensor type part is If you can buy it at autozone, dont use it.

 

If you are seeing 0 mV on an O2 sensor, and the PCM is in closed loop, the PCM is reading that as seriously lean. Hence the code. If its a "false" lean condition, the plugs won't show signs of running lean, because the PCM will be pouring in extra fuel the PCM doesn't need. The O2 sensors should never sit at a fixed rate, once the PCM enters closed loop. On the other hand, it would be normal for the O2 sensors to start at 450V cold, then drop to ~0 mV as they warm up, in open loop (particularly when you have a functional AIR pump). After the sensors warm up, the coolant exceeds ~120*-F and the 205-second timer times out, the PCM will enter closed loop and the voltage should swing quickly back and forth between 0xx and 9xx mV's.

Most people find that the OEM AC/Delco (now Delphi) O2 sensors are more reliable.