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Discussion Starter · #1 ·
On my 06 Express 3500

I’ve got codes P2A04 and 300, which is bank 2 sensor 2, and misfires detected. so I’m gonna try throwing a new sensor in.

First off, do you think that’s a good place to start?
Bank 2 Sensor 2 that’s passenger side behind the cat?
Are there four sensors?
Should I do all four at once?

Thanks!
 

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‘01 Silverado 2500HD 8.1/Allison 5sp xcab long bed
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Before spending any money, I would recommend swapping the downstream sensors and see if the code switches with it. If it does, then yes, replace that one. It would indeed be passenger side post cat.

There usually are 4 on V8 &V6 engines.
 
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The P2A04 code is set when the computer does not see a response from that O2 sensor.
The problem could be a bad sensor.
If could also be a burnt, broken, O2 sensor wire.
It could also be working fine and properly reporting what it detects, which could be too much oxygen.
There is a possibility that when you fix the misfire you will have also removed the O2 code.

I'd be looking for a vacuum leak on the passenger side of the engine.
 

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Discussion Starter · #4 ·
Before spending any money, I would recommend swapping the downstream sensors and see if the code switches with it. If it does, then yes, replace that one. It would indeed be passenger side post cat.

There usually are 4 on V8 &V6 engines.
Oh yeah that’s a good idea. Thanks
 

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Had two dual exhaust Taurus' (1996 and 1998) some years back. On one of them I got one code pointing to a downstream sensor so I replaced it. Three days later got another code for the upstream so I replaced it. A few days later I got the downstream code for the opposing bank. Said funk it and just replaced both. A month later the other Taurus kicks out the downstream code for one bank so I replaced all 4. No more codes. Now when I get any O2 sensor related code I replace them all and be done with it.

To answer your question I don't think its important to replace them all at once. You only need to replace what's shot. I just had this one experience where they all seemed to go bad at about the exact same time. May have been a fluke. I've had a number of cars since then and its been my experience that the O2 sensors are good for about 120,000 miles.
 
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