Hi all,

First, I have read the couple of posts regarding the code, but would like to ask if anyone has had the code disappear indefinitely? The code popped up on Friday and my SES light turned off on Tuesday. After reading the TSB I hope this code truly stays away as the TSB calls for replacing the Front Tube Assembly (does this include the Pre-Cat?) and one of the O2-Sensors. I have already replaced the Pre-Cat, all 4 O2 Sensors, and Muffler in the past 40-50k miles (I am currently at 143,000 miles) and seriously doubt that I'm willing to spend another $600 to replace the pieces the TSB calls for.

Thanks for you input.

 

P0420 is the Bank1 catalyst. It is located in the y-pipe, the one you have not replaced yet. The code will come and go, but will never disappear until you replace the bad part. Common issue on 2K Max, lots of info around here on this.

 

The code stays in memory. When a misfire occurs, it stores it in the computer, until it happens a second time. When that second time comes around, it will turn on the MIL. When your "Check Engine Light" comes on-that means it(the ECU) sensed a fault for just a tiny moment in time. If it's flashing...then it is now time to stress. After 4 complete drive cycles, if the fault has not re-occured, the light will turn off. Like I said-the code will stay in memory, not disappear. If I'm not mistaken...part of that TSB also states to reprogram the ECM. So it's kinda tough to say where to go. To get the next level of programming-I'm not sure if Nissan will let you get the flash without purchasing their front tube assy, or not. But basically-they're gonna get your money. That computer is gonna need the new software one way or another. I went through the same thing on my 2001. Buy a new Y-pipe(Cattman or Warpspeed), disconnect the negative cable while you do the work, and cross those fingers!

 

I had the P0420 code for a few months that went away when I swapped in a cattman y-pipe.

 

Well as I said in my original post I'm probably not going to spend upwards to $600-700 to replace the Front Tube assembly and o2 sensor. I feel if I do that then soon enough the rear cat will need replacing and my total outlay for this exhaust in the past two years will exceed $2500....simply to much money for exhaust repairs on a car with 143k miles. I'll drive it as is and prepare to get another vehicle. Currently, the light has been off for 3 days and the car has always run fine.

One last note ...the ECU was updated with new software quite a while ago. I'm assuming it's okay and there truly is an issue within the front pipe/O2 sensor, or it was simply a fluke and will not reappear. On my next trip into Nissan mechanic I'll have them check the version of the software in the ECU.