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Discussion Starter #61
All looks good now. How about the B1S1 voltage--is that back around 2.25V? Your case is important since it proves that in the 2nd generation Murano, the PCM can use the signal (or lack thereof) from the downstream O2 sensor for fuel trimming. In a lot of cars, the downstream sensor is used solely for monitoring the condition of the catalytic converter. I still don't know why the PCM was deferring to the downstream sensor when the upstream sensor was working--just doesn't make sense to me. I really would have liked to see how the PCM would respond if you disconnected the downstream sensor so it wasn't receiving any signal at all. But anyway, it's done and fixed.

BTW...which way did you end up taking it out?
Well first of all thanks for all your time helping me try to resolve, that was a tough one.
When I was talking with the Nissan Tech he said there is a “loop” that takes place between the sensors, so if the sensor 2doesn’t have any voltage resulting in not sending the loop signal back it causes the rich condition. My assumption would be that even if I disconnected and tested we would have got the same results as most of the results I provided were without voltage coming from sensor 2.

Now replacement of the bank 1 sensor 2 process. First off, it is a REALLY tough job. There is no room what so ever around the sensor to get a ratchet in there. You need to use one of those side sensor sockets which itself was extremely hard to get it on with literally 1/2” of space for the torque itself. There is a nut on a bracket that you need to remove which will give you 1/4” extra to get the socket on. I finally got it on, Put an extension on to the breaker bar and first attempt I literally snapped the extension tip right off.
Switched to another smaller extension and was finally able to get the seal to break.
Now for the connector. Thinking the worst was over and was sadly mistaken. I was able to get my hand (no way you are getting two hands in there) on it from underneath, but the clip holding it in was not allowing me to release it no matter how much force I used with my thumb while using my other fingers to pull it out.
So had to try to get at it from the top with no luck as it is buried by the firewall. I thought I couldn’t get more pissed after how hard it was to get then sensor loosened 😡 . So, my only hope was to remove the whole wiper cowl again 😡. Finally had more access to it, but even after several attempts with a screw driver to push the clip down it still wouldn’t give. It must have been at least a half an hour fighting to get it unplugged, but finally it released. Installing the new one and putting everything back together was easy, but man these two bank 1 sensors are brutal to replace.
 

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Discussion Starter #62
Well first of all thanks for all your time helping me try to resolve, that was a tough one.
When I was talking with the Nissan Tech he said there is a “loop” that takes place between the sensors, so if the sensor 2doesn’t have any voltage resulting in not sending the loop signal back it causes the rich condition. My assumption would be that even if I disconnected and tested we would have got the same results as most of the results I provided were without voltage coming from sensor 2.

Now replacement of the bank 1 sensor 2 process. First off, it is a REALLY tough job. There is no room what so ever around the sensor to get a ratchet in there. You need to use one of those side sensor sockets which itself was extremely hard to get it on with literally 1/2” of space for the torque itself. There is a nut on a bracket that you need to remove which will give you 1/4” extra to get the socket on. I finally got it on, Put an extension on to the breaker bar and first attempt I literally snapped the extension tip right off.
Switched to another smaller extension and was finally able to get the seal to break.
Now for the connector. Thinking the worst was over and was sadly mistaken. I was able to get my hand (no way you are getting two hands in there) on it from underneath, but the clip holding it in was not allowing me to release it no matter how much force I used with my thumb while using my other fingers to pull it out.
So had to try to get at it from the top with no luck as it is buried by the firewall. I thought I couldn’t get more pissed after how hard it was to get then sensor loosened 😡 . So, my only hope was to remove the whole wiper cowl again 😡. Finally had more access to it, but even after several attempts with a screw driver to push the clip down it still wouldn’t give. It must have been at least a half an hour fighting to get it unplugged, but finally it released. Installing the new one and putting everything back together was easy, but man these two bank 1 sensors are brutal to replace.
I will check the bank 1 sensor 1 voltage. After all of this, the root cause may have just been the bank 1 sensor 2 even though all root cause material in the FSM and on the internet point to replacing the A/F bank 1 sensor 1 $400 later just for the sensor. It would probably be close to 1k for the dealership to replace with labour. Then another few hundred for the other sensor. It wasn’t a fun job, but is satisfying when the outcome solves the problem.

Still love this MO, but think I have pretty much replaced everything on this SUV beside the tranny, engine and myself over the past couple of years. I am at 336,000km’s (209miles) now. Once one of those go I am done. I will most likely switch to buying a Lexus RX350 to stay with a v6 or a RAV4 4 cylinder (lots of room to work). My decision will be based on proven reliability. My wife is still driving a 2004 Honda CRV and this thing is like a cockroach and will not die 😂. It is insanely reliable. I just ran all the different scans on it just to see the results and it came back super clean. Almost 20yrs old and I have only needed to swap all the fluids regularly, tie rods/ball joints once and brake pads. I know first hand how reliable vehicles (Honda/Toyota) made in Japan are.

Unfortunately for Honda I wouldn’t touch the new CRV’s now and only because of the 1.5’s direct injection engines which have the oil/gas dilution issue. They are going to have engine issues as the carbon builds up.
 

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How many miles do you have on your 2004 Honda CRV?
 
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