left bank o2 sensors reading 0, P0171, P0174

[jwalker1970]

I just replaced a transmission on a 99 Explorer 4.0L (OHV vin X)

After about 100 miles of driving I got P0171 and P0174, indicating lean on bank 2.

I used my MT-2500 to read 02's and they read as follows as you throttle up & down:

02S11 & 02S21 (R side) fluxuate between about 200 and 800 (rich-lean OK)

02S12 & 02S22 (L side) are pegged at 0, no movement whatsoever.

I unplugged front 02 sensor on R side (bank 1) and it pegged to zero.
I unplugged rear 02 sensor on R side (bank 1) and it pegged to zero.

However, there is only one 02 sensor on bank 2. It stays at zero whether plugged in or not.

Normally I'd suspect a bad 02 (bank 2, sensor 1), but having both Left sensors read zero is throwing me for a loop.

Thanks in Advance!!

[danielsatur]

Suspect bad plastic, rubber, or seals causing unmetered air leaks on Intake, EGR, or PCV systems.
Try doing a smoke test -
www.youtube.com/watch?v=FfiQ7qWiG-M

[shorod]

P0171 would indicate Bank 1 is too lean, P0174 indicates Bank 2 is too lean. Since you have both codes, you should be looking for something impacting both banks. The voltages you are seeing on the oxygen sensors don't make sense for such a code.

Have you checked the short and long term fuel trims to see if they align with lean codes on both banks?

-Rod

[jwalker1970]

Replaced D.O.A. Left bank front sensor, cleared codes.

Fuel trims dropped back to normal, sensors cycling rich/lean, no check engine, customer drove 500 miles.

[danielsatur]

What's D.O.A. ?

[shorod]

So you didn't have to replace the Dead On Arrival (DOA) B2S2 sensor as well? You previously indicated it was shorted at 0 volts as well.

-Rod

[jwalker1970]

there's no downstream sensor on the drivers bank, confirmed with another 4.0 explorer