# 2002 Nissan Sentra Po430 SES code



## samkal (Jan 8, 2009)

Hi Experts,
I got Po430 code last year in the month of October and then I cleared the code and came back after a month . Drove car another couple of months with code on and no issues with power etc and car was ruuning smooth. I cleared the code Febuary and came back in March. I finally took it to the Dealer in May and after diagonstic test , the dealer told me that it requires new cat converter, may be 2 oxygen sensors as well and the total cost would be around $1700. After diagonstic test I did see SES light on and not susre whether the dealer cleared the code or test fix it. Today after 3 and half months I drove the car early in the morning and SES came on.Today weather was cold , like it was last year and PO430 came on. Does this has to do something with weather? Please advise what are my options for this car which has around 117k m on wheels.

P0430 - Catalyst System Efficiency Below Threshold (Bank 2)

Description
Indicates Bank 2 catalyst system efficiency is below the acceptable threshold.

Thanks,
Sam


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## smj999smj (Jan 1, 2006)

P0420/430 codes are efficiency codes...meaning that the media inside the catalyst is not breaking down the exhaust gases like it should. This is based on the readings the ECM receives from the front and rear oxygen sensors. On vehicles with front and rear catalytic converters, the front converter will always be the "monitored" converter. There are a couple of things that can cause catalyst codes, but when the only code stored is the P0420/430 code and there are no exhaust leaks, the catalytic converter is the culprit almost all of the time. As far as the oxygen sensors, chances are they are okay, but sometimes they will rust into the converter and be difficult to remove and/or the threads can become damaged; you won't know until they are removed. Also, they do lose some efficiency over time. As far as the $1700 quote, that's a bit high. If it were mine, I would order a name brand, direct-fit, aftermarket converter (ie Bosal, Walker) from Rockauto.com, as well as new Denso or NTK oxygen sensors, and replace it myself. If you don't have the tools or ability to do it yourself, you could always have an independant shop do it. I would get some additional quotes, at least.


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## samkal (Jan 8, 2009)

Thanks for your response. I am getting only PO430 code and local shop mechanic suggested to replace oxygen sensor only.My next car emission inspection is next year, is it ok to drive car with SES on? please let me know,


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## smj999smj (Jan 1, 2006)

I doubt that replacing the oxygen sensor is going to fix your problem; a bad oxygen sensor will usually set an oxygen sensor trouble code. If you had both oxygen sensor and catalyst codes stored, I would suggest just replacing the oxygen sensor, erasing the code, then address the converter if the catalyst code re-occured. Since you only have the catalyst code, it is likely that your oxygen sensor is fine and your catalytic converter is faulty. As far as driving with the SES light "on"....the answer is both "yes" and "no." If the catalytic converter is inefficient, you will not do any mechanical damage by continuing to drive it as is. However, if the SES light is always "on" because of the P0430 code, you will not be able to know if there is another code that has been set because you will always assume that the code if for the inefficient catalytic converter. If the other code is related to something that could potentially cause mechanical damage in the long run...like a "system-lean" code...than potential damage could occur. Normally, those types of codes will be associated with driveability symptoms (surging, hesitation, etc.), but I can't speak for every possible potential problem you might have.


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## rogoman (Dec 16, 2004)

samkal said:


> Thanks for your response. I am getting only PO430 code and local shop mechanic suggested to replace oxygen sensor only.


Also check for the following:

 Exhaust pipe leak
 Intake air leaks
 Injectors
 Injector leaks
 Dirty spark plugs
 Improper ignition timing


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## samkal (Jan 8, 2009)

I took the car to the local garage and the mechanic said that the SES code is PO430 and it appears the sensors are faulty. When I asked about faulty cat converter, he mentioned t then the code should PO420 and PO430.Is he correct? or he just want me to first spend on the sensors and the cat converter.


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## smj999smj (Jan 1, 2006)

No....P0420 and P0430 refer to different banks (I know it's an inline 4 cyl, but Nissan refers to two of the cylinders as Bank #1 and the other two as Bank #2 and uses a total of 4 oxygen sensors: upstream & downstream Bank #1 and upstream and downstream Bank #2). It's possible to have a bad catalytic converter and only the code for one bank set. That said, I am not there diagnosing the car and I cannot tell you whether you have bad sensors or a catalytic converter. It's hard for me to dispute a technician who is actually working on the vehicle in question whereas I'm only answering questions on a forum. I can only tell you what my experience has been as a Nissan technician in the past. You need to weigh your options and choose whether to replace the sensors, the converter, both or do nothing. Keep in mind that, for what it's worth, the dealer told you it needed a converter, as well. Good luck and let us know how you make out!


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