I apologize ahead of time. I have been on here for a while and I have been doing my time for researching but I have come to a point where I am not sure which area to tackle first. I recently purchased a 01 Maxima SE. It has 264,XXX miles on it. It appears to have been taken care of decently but the previous owner openly stated he had no mechanical skills or knowledge about vehicles. After replacing the starter and condenser fan motor I still have some codes that are still popping up. They are P0159, P0158, P0139, P0505, and P0720. There was another code here recently but I can not remember it. Sorry. I am wondering which one I should try tackling first. The only issue that I am appearing to have at this time is with initial start up. It wants to die after attempting to start it but if given a little gas it will stay running and won't "choke out." Other than that the car appears to be running ok at this time but I don't want to let it go for too much longer and cause issues. Any advice or suggestions would be greatly appreciated. Thanks.

 

Read this
http://boredmder.com/FSMs/Nissan/Maxima/2001/EC.pdf

The first to tackle is the code P0158, P0159 P0139
:this code refer to your precat
P0158 &P0159: O2 Sensor with Red Wire (precat near the radiator)
P0139: O2 Sensor with white wire (pre cat near the firewall)
How to fix
Replace the precat: OEM Genuine Nissan Precat: Cost $599.00 each parts only
:OEM Aftermarket Precat : Cost $299.00 each
Another way: Install headers and 02 sim
The cheapest way : is to gut both precat and install nonfouler to the two secondary 02 sensor (white and red wire) or 02 SiM

Read this for O2 nonfouler
http://www.energeticforum.com/renewa...n-foulers.html

 

I think your IAC/ECU is shot..If you search the forum for p0505 you will see many many posts regarding this issue. This is releated to your starting and shutting off issue. P0720 is the Revolution sensor on the transmission right near the drive wheel.

 

I am confused? Why would I have to replace the precat when the codes states that its the sensors are going bad?

 

So you think it is better for me to start with the P0505 and P0720 codes first then deal with the other codes next? Just trying to fix problems in a simple system so that I am not fixing and changing anything that doesn't need to be changed. Wish I had money to just throw around though .

 

Secondary 02 sensor monitor the condition of the precat.

 

Secondary O2 means Precat soon to fail or already bad......Im going to gut out the precats in November when I go to Florida for a week, already talked to my mechanic there, while he replaces the rear arm bushings, I will gut the PreCats,