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Discussion Starter · #1 ·
Hey all,

I had my engine replaced about 1000 miles ago. It had a blown head gasket, they replaced it, but some part they used was faulty, which somehow messed up the engine, so they replaced the whole thing (free).

Anyways, I'm getting these two codes now. Since these two codes deal with different banks (sides of the engine), I thought maybe they had plugged in the O2 sensors into the wrong clips, but it *seems* like they're in the right place. I say this, because it's hard to tell exactly which sensor is clipped into what. Plus, they replaced the engine a while ago, so it seems like it would have come up sooner.

P0430: Catalyst System Efficiency Below Threshold Bank 2
P1143: Heated Oxygen Sensor 1 Lean Shift Monitoring Bank 1

1. Is there a way to tell whether the O2 clips are plugged into the right plugs?
2. If they are plugged into the right place, how can I diagnose whether it's the O2 sensor or the cat? Or both?

Here is a pic of the clips/plugs I'm talking about. I can see the red and blue-wrapped wires, but aside from that, it's hard to see what's going on.

Some background: crappy gas mileage (~13-14 mpg, usually around 18mpg), power is on the low side, but not really bad. Mechanic is good, I trust him.

2002 Xterra, V6, not s/c
245k original miles, 140k on the new engine.


I appreciate any help you can offer.

Thanks,

-stu
 

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right down stream is gray covered right upstream is black covered left downstream is red left upstream is blue make sure you got it right

make sure your blue runs to drivers fron o2 and red drivers rear and black pass. front grey pass rear
 

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other than that there maybe an exhaust leak somewhere
 

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Discussion Starter · #4 ·
Well, it seems it wired up properly... Must be something else. Any way to verify an exhaust leak?
 
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