SES light on. Code read P0138 - which is O2 sensor before cat. There are two sensors before the cat and one after. EACH ONE costs $309.95 at Autozone. Guy there said some have been successful cleaning the sensor since build up on the sensor tip causes a faulty O2 reading. Is there a way to find out WHICH SENSOR IS FAULTY (firewall side or radiator side)? Guy at AZ said to remove it and clean it with a wire brush and some carb cleaner. If I don't know which one is faulty I don't want to ruin the still-good one buy putting solvent on it. Will solvent mess them up?

 

How many miles do you have ? This should be covered by the 5yr 60K mile powertrain warranty. As far as cleaning goes, best way to clean it would be getting a propane torch and heatting up the cat to get rid of the carbon inside. It works, but mostly on old feedback carburated cars like late 80 early 90 Chevys.

 

My FSM says its the sensor after the cat. Like Mike stated it should fall under powertrain, even Emissions warranty depending on you mileage. Nissan probably sells them for less. I got my front o2 sensors for around 120.00 each.

 

I have 101,000 miles on my 03 Max (mostly highway miles) so no warranty coverage anymore. Please verify that code "P0138" is which sensor (before cat-firewall side or radiator side?) OR (After cat?).
Clean the cat with a propane torch? Should I avoid solvents?
Also, where did you buy O2 sensors for $120.00

 

DTC P0138 relates to the rear o2 sensor in Bank 1. This is from my FSM. Keep in mind that I have a 2000 Max. Since you have a 2003 I believe you have four o2 sensors, Two per bank, two front and two rear. Bank one should be the one on the firewall side. So it will be the very bottom one on the firewall side. Keep in mind that the rear o2 is used to monitor the Cat and is not used for engine control under normal conditions unlike the front 02 sensors. Talk to DaveB at Southpoint Nissan in parts and tell him you are a Member of maxima.org. He gives discounts. I got my front o2 sensors at a local dealership and they give me 20% off.

 

I just had the exact same problem on my 02 SE Auto. The dealer replaced both rear O2 sensors and reprogrammed the ECU. They charged me nothing because this is covered under the emissions warranty. There is a TSB to cover this. Its NTB02-051a.

 

It's not. A number of people have tried, and unless you're very lucky (ie. the dealer is ignorant) then you won't get it covered.Damn, that's lucky. A ton of people on the forums have had to pay for their own O2 sensors. I tried myself to have one covered under 60k or emissions and both dealers I called said nogo.

 

It shows you in this TSB which sensor your code applies to.
http://maxima.theowensfamily.com/tsb/NTB02-051a.pdf

 

I do'nt have my FSM on me, but I'll see if I can look it up for ya this week...

Also, even the most expensive dealerships around here have O2 sensors for less than $150, so I'd say do some shopping around... $300 is nuts...