Oxygen sensor Bias Voltage Problem

Hello,
I have a 2004 frontier 3.3l supercharged with 2 codes P0132 and P0152 code, (high voltage on both upstream sensors)
My bias voltage reading on the scanner for upstream o2 sensors is 0 when the engine off key on, but the reading on the scanner for both downstream sensors is 300mv, im guessing i should also have a bias voltage of 300mv on both upstream sensors.
The weird part is that if i measure the upstream o2 signal wire with a voltmeter it shows 300mv.
I dont understand why the voltmeter shows voltage but not the scanner.
Has anyone had or seen this issue?
Both downstream sensors show voltage with multimeter and scanner

Any help would be really appreciated.

The weird part is that if i measure the upstream o2 signal wire with a voltmeter it shows 300mv.

Was this measurement taken with the sensor plugged in, or sensor unplugged? It's possible that the sensors were fully warmed up when you were looking at the scan data, causing the sensors to pull their signal bias voltages to ground like they should. Once the sensor is unplugged to take a voltage reading, then the bias comes right back.

How are the O2's and fuel trims performing at idle and during a test drive? Are there any fuel control problems? If you can grab the Freeze Frame data for either P0132 or P0152, it might give you a clue as to what the issue is.

Hello, the signal was measured when sensor was plugged in and unplugged as well.
Multimeter always had 300mv in both cases, but scanner would always read 0.
Freeze frame data for p0132 Fuel trims were at -25 for short term and 0 for long term.
No freeze frame for p0152.
Thank you.

Hello,

Short term fuel trim indicates a rich mixture but i have only seen the upstream 02 range from .2 to .6v
Thank you.

This reading was in closed loop mode,
What should the bias voltage be when engine off key on?

Scanner only reads bias voltage for both downstream o2 sensors(300mv)
Downstream o2 reads 0.

Is this how it should be?

Thank you

Both downstream o2 sensors have 300mv when sensors plugged in and unplugged as well.

Both upstream sensors have 0 volts when sensors plugged in and unplugged.

P0132 and p0152 is code for upstream sensors (B1S1 and B1S2).
I haven't replaced the sensors because following Scanner Danner videos, if Bias voltage is not present most likely O2 sensors are fine. Also, the sensors read correct resistance per the book.

Just need to make sure there should be a bias voltage.
Thank you.