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2007 3.5 L V6 with both bank 1 and bank 2 sensor 1 failures. The dreaded three lights + problem showed up.
Codes for the first O2 sensor on bank 2. Replaced it. codes for bank 1 show up, replaced that one. The O2 sensor came out ok after I used a long 3/8 extension and O2 socket as a wick to allow PD blaster to get down on the threads on the manifold. Tough but it came out without damage to the threads. Replacement was doped with anti seize before putting it back.

Both sensors are new Denso parts of the right part number(s).

What I have now is the car will run for about 24 to 48 hours and then set the code P2195 "biased stuck lean" for B1S1.

I stuck the code reader on the system and set it to show me live data from the ECM about the O2 sensors. What's odd is the ECM shows the B1S1 voltage constantly cycling from 0.00 to 4.99 volts quickly. I don't get any P codes from the ECM showing issues from that.

When I tied a FLUKE volt meter in to the wire just upstream from the connector at the O2 sensor I see a steady 3.32 volts. That matches what I see and read from the B2S1 O2 sensor.

Do I have a bad ECM here or is it possibly wiring? I think but may be wrong that the low voltage feed comes from the ECM and should be showing the flapping I see in the diagnostic tool if it was real.

Trying to figure out what might be wrong here or if it's not worth the fight to save the car. Can't keep the car licensed here in this state unless it passes an emissions check which it won't with the cycle time too short or the CEL on with active codes.

thanks for any kind of ideas

-bill
 

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What's odd is the ECM shows the B1S1 voltage constantly cycling from 0.00 to 4.99 volts quickly.

When I tied a FLUKE volt meter in to the wire just upstream from the connector at the O2 sensor I see a steady 3.32 volts. That matches what I see and read from the B2S1 O2 sensor.
The sensor should have a constant voltage across it (as you read with the Fluke). As the A/F values change, only the current passing through the sensor changes. The ECM converts the current changes to the voltage changes that you see on your test equipment.

Are you saying the B2S1 voltages do not change on the code reader?

Try unplugging the B1S1 sensor. Without current flowing through the sensor, the voltage on the code reader should be fixed at about 3.8 volts. If it continues to fluctuate you may have a defective ECM or a wiring problem.
 
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