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Ron Z.
Ron Z., - Nissan Tech -
Category: Nissan
Satisfied Customers: 19052
Experience:  18+yrs experience. State Inspector and Nissan Diagnostics
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I've got a P0420 Bank 1 code showing up on my 2009 Nissan

Customer Question

I've got a P0420 Bank 1 code showing up on my 2009 Nissan Murano SL. I was going to replace the O2 sensor but after talking to a guy at the parts store, he says there are 2. Any way to check which sensor it is?
JA: Have you located all of the vehicle's oxygen sensors? Are the wires leading to and from each intact and in good shape?
Customer: I've located one, and it looks like it's in the back of the engine. I haven't spent a lot of time with it, but I was going to try to take it out and clean it, check it out, and then see if that helped.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: If it was just an O2 sensor, yeah, I was going to do it myself. I've really only had time to check the code after the check engine light came on, and then use google to try to find more information. I just thought I would check to see if anyone knew if there were two sensors or just one
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Nissan Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Nissan
Expert:  Ron Z. replied 1 year ago.

Unfortunately, the P0420 is a fairly straight forward code, and a fairly common problem. This code points to a failing Catalytic Converter for Bank1 (the side of the engine closest to the windshield). The Oxygen Sensors measure the amount of emissions in the exhaust going into, and then out of the converter. When they see that the converter is not "cleaning" the exhaust enough to meet specs, the Converter is deemed "below threshold" and the P0420 is set. Make sure there are no current cylinder misfires. Make sure there are no leaks in the exhaust system. Which, if there were, you should be able to hear. Sounding like a repeating "tick" or "puff" from the exhaust. Usually more prodominate when the engine is cold. Make sure to include the exhaust manifold when checking for leaks/cracks. If these check ok, then most commonly, the Converter is "on it's way out" and will need replacement in the near future. Keep in mind, you will need a replacement converter that meets specs. Those "universal" or "discount" converters sold at some after market parts stores do not meet specs, and will not cure a P0420.

If you would like to try and replace the oxygen sensors anyway, here is the image location view of the Bank1 sensors:

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Expert:  Ron Z. replied 1 year ago.

If there's any other information you need, or something I missed in my answer that you wanted addressed, please feel free to ask!

Expert:  Ron Z. replied 1 year ago.

Hi! Ron Z again. I noticed this thread was still open and you did not leave a rating , so I wanted to check in and see if there was anything else I could do for you on this issue? Did you have any other questions? Was there something I missed that you wanted addressed? If you have no further questions and simply forgot to leave a rating, please take a second and use the stars at the top of the page to rate our Q&A session. Thank-you!