Oxygen Sensor Question

Henry1210

New Member
Jan 19, 2021
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Connecticut
Hi All, Probably a common question but I am unable to find through search.

I have an 03 GT, all stock.

Getting two codes P1151 lack of HO2s21. P1131 lack of HO2s11. From what I'm reading these are bank 1 and bank 2 oxygen sensors, but are they the upsteam or down stream sensors?

Also, which side is bank 1 and bank 2? Is bank 1 driver side?

Thanks for the help
Henry
 
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weendoggy

Member
Jan 14, 2019
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Aptos, CA
Bank 1 and Cyl. 1 are on the passenger side. Think right or left viewed from the driver seat, not the front of the car.
Upstream is before the catalytic converter and the downstream is after the converter. The downstream is verifying the upstream is doing it's job. Save some time and replace them all (4) if one is bad.
Strange both upstream O2 are saying lean condition. You may want to start by checking for vacuum leaks, MAF fault, fuel pressure, etc. which can definitely cause the problem.
 
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