I have purchased a used 2001 infiniti i30 couple of months back and it expired the dealer given 1000 mile warrenty. Now, the SES light on and after checking with the OBD, it showed that P0420 - catalytic efficiency low (bank 1). And also the detailed codes showed that 1) Catalytic - Not Ready2) Emission - Not Ready3) 02 Sensor - Not Ready4) Heater - Not ready. All other codes shown either Ready or NA.The local mechanic inspected my vehicle and told that the catalytic converter needs to be replaced. I have some questions regarding that and any reply would be greatly appreciated.

1) There are 3 catalytic converters available for Front Wheel Drive Infiniti i30. They are front, rear and center units. If the code is P0420, which one I need to buy? The mechanic says it is the center unit. He told that the rear unit is not attached with the sensor and the code says it is bank1, so it is the center part. Is it true?

2) If I replace the center unit, all the 4 problems will go off? or only the catalytic problem will go off?

3) When I cheked for these parts online, the center unit is availalbe with most of the sellers for $310. But, When i read the problems posted by other people in this site mentioned that the catalytic converter replacement costs around $2000 - $3000 range. Do I need to purchase any other parts along with this center unit catalytic converter to get rid of all these problems?

4) Finally, some where I have read that, reset the car computer. After the light came, I am feeling the difference in driving. I need to push the gas hard and engine/ car is making more noice. I feel there is a problem with the exaust / emission system and I am okay to replace the parts if it is going to cost in $300 to $500 range.

Please advice.

ThanksPeter

How many miles on odometer? Nissan has a special warranty on cats [8/80k] and emission components read your warranty booklet and owners manual.

Aftermarket cats are very thin on platnium and rhodium and thus may only last a few years at best.

Platnium went from $600/oz to a high of $2700 this year now down to $1230 this weekRhodium went from $350/oz to $10,000/oz now $7500Roughly 90% of all platinum supplies come from South Africa and Russia.Rhodium was cheap in 1994-2001 and used frequently in quanities.

Hopefully you can see why cats are being stolen and aftermakets have little in them.

Modern OEM cats have 3-7 grams of exotic materials in them [31.1 grams to precious metal ounce].

Japanese big cats have twice as much as domestics and those on old V8 may have up to 11 grams each.

Those cats go out all the time. You can try an aftermarket, however it might not last. As far as your OBDII SRTs, they may be "Not Ready" due to the code having been cleared. Anytime you clear out a code the system resets and the ECM has to go through a series of self tests. In regards to your lack of power, I would lean to a mass airflow issue. It may not be setting a code but can cause a rich or lean running condition. From your discription of "noise" I would say it is running lean and causing excessive spark knock. Have your mechanic check your airflow alpha (fuel trim) to determine if it needs a MAF sensor. Also, if it does need a MAF sensor, remember to replace the air filter with a new one and vacuum any debris from the airbox.