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6Bucs, ASE Certified Technician
Category: Nissan
Satisfied Customers: 981
Experience:  Master tech with 18 years dealer experience
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03 Xterra 4X4 automatic V6. had code PO430 and PO158. 4 new

Customer Question

03 Xterra 4X4 automatic V6. had code PO430 and PO158. 4 new o2 sensors. cleared codes. have driven 180 miles. scanner shows no codes but shows o2 monitor incomplete. how do I fix this to pass emissions inspection.
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: read toi message, 4 new o2 sensors
JA: Are you fixing your Xterra yourself? What have you tried so far?
Customer: read the message
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 1 month ago.
Category: Nissan
Expert:  6Bucs replied 1 month ago.

Hello and thank you for your question. My name is James.

The p0430 indicates the catalyst for the left bank of the engine has reached its efficiency limit. The catalytic converter is made up of some precious metals inside it, platinum for instance, that react with exhaust gases to clean them. When these metals "wear out" they don't have the capacity to clean the exhaust anymore. The engine management computer will set a code when the catalytic converter has completely failed, however it won't pass the monitor test if the cat is functioning just keeps waiting for it to perform up to standard. Yours has worn to the point where the computer identified a failure at one point. Once this happens, there is no way to recondition the catalyst to reach OBDII standards again.

The short answer is that the left bank catalytic converter needs to be replaced and then the vehicle driven about 20 miles on the freeway for the monitor to clear.

I hope this has been helpful.