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Hi all. I've replaced all 3 O2 sensors on my Subaru B9 tribeca they reset the computer and about 2 days later the check engine light comes back on. The code it throws is always the same O2 sensor the 1 on the front of engine. No one can seem to figure out what the problem is or how to fix it. Any suggestions would be great
 

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06 B9 Tribeca
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As far as I know. I took it to the shop where I bought it from
Hi, thanks for joining. Please add your model year to your signature or profile. This is a forum rule. Assuming that you have an 06-07 Tribeca based upon your B9 comment?
 

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06 Tribeca 3.0L H6
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As far as I know. I took it to the shop where I bought it from
Ok, to my knowledge, O2 sensors send signals directly to the ECM. If a wire is broken somewhere along that path, the ECM isn't getting what it needs and throws a code.

Another possibility could be that you have a leaky injector that is putting unburned fuel into the exhaust that the sensor is picking up and setting a code.

The shop where you took it should be able to run a diagnostic test to verify that the ECM is actually getting the signal from the sensor (not just a code reader).
 

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V6er Version 2
Facelift (EZ36D, 5EAT TG5D), MY2008, 7seat Limited (no DVD, no NAVI)
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343 Posts
1) there should be 4, not 3 lambda sensors (AF, whatever you call them).
2) may be it is time for "second opinion". "shop who sold it" ...... they have their own agenda...
3) error code would be good to understand what kind of error we are talking - one thing is " rich", and another is " short to ground" or "short to +12".
 

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Someone with more knowledge than myself may want to chime in, but I know Subarus are finnicky with certain aftermarket parts. If the sensors are not genuine Subaru this could cause an issue, just raising a potential issue, not saying this is the actual problem.
 
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