P0158 & P0159

[Towncivilian]

I was driving to my college campus 30 miles away this morning. I was on the highway going 75 set on cruise, and my SES light illuminates about halfway through the trip. I pulled the codes a few hours ago and it was a P0158 stored, and P0158 & P0159 pending. These indicate one of the rear oxygen sensors. I cleared the codes, then drove at relatively high RPMs around town real quick for 10 minutes and the code did not reappear. I will take the highway back tonight. Is this something I should worry about, or is it just a fluke? The FSM says that the rear oxygen sensors are not used unless there is a problem with the upstream sensors, if I'm interpreting it correctly. I believe all the oxygen sensors are original at 128,1xx miles. Gasoline is 93 octane, full tank when I left.

[Towncivilian]

The SES light did not illuminate on the trip back. I will pull codes to check for any pending ones tomorrow.

[Finkle]

You think it was just a fluke?

[Towncivilian]

I sure hope so. A bad O2 sensor would sure be an annoyance after getting my oil pan seals and rear main seal replaced to the tune of $1600... a rear O2 sensor is around $150. But if the sensor ends up bad, I can ignore it for a while since there are no emission regulations in Florida, and as I mentioned, the upstream O2 sensor is the important one. My mother's '07 Altima has had a bad rear O2 sensor for 10k+ miles with no ill effects thus far.

[ARKQX33V6]

O2 sensors have a lifespan, heated O2 sensors have a lower lifespan.

Heated by an external power supply the heated sensors do fail faster because of voltage failure to the heater, The heater can fail, the wires can fail, more problems.

The non heated sensors can also fail from excess heat, coatings of crap, loose fittings, bad wires bad or worsening connections.

The ECU can be giving or receiving faulty info.

The sensor could be old and slowing down in actual reading and the output from that sensor and the input to the ECU become out of step and the lag produces a very lean or very rich condition at a given point then the MIL is set.

What you have done is proper, now be patient, the MIL may come back or not. You are using 93 grade gas do you need that grade as per design? Or is the engine knocking with a lower grade? Using high test where none is needed will create a high carbon condition and then force you to require 93. Use the grade recommended by Nissan.

A retarded O2 sensor may respond to a cleaning, but that requires as much work as replacing it. To simplify replacing use high temp RTV to stick the leads unto the body without drilling holes, when it sets up it will hold the leads.

Your odometer reading indicates the end is near for the O2 sensors, but keep using them until the MIL KEEPS INDICATING A NEED TO REPLACE.

When reset and then a restart to drive away the MIL comes right back, it's time.

[yeldogt]

The rear sensors are checking the catalytic converter -- the front sensors are making engine adjustments. That is a simplified description of the operation of the system -- but all the sensors are always working. Pathfinders had an issue with the software in the control for the 02 sensor heaters -- this was included in a service program for the rear sensors. The software was changed to alter and shorten the operation of the heaters in the rear sensors. The heaters get the sensors up to the proper working temperature so they can adjust the emissions of the car when you start from cold -- older systems have to wait for the engine to heat the exhaust and then the sensor -- so for all that time the sensors are not working.

The heaters in the sensors are often what fails first -- so you don't normally have a drivability problem .... the actual sensor is still working. The old software kept the heaters "on" too long and they would burn out -- causing the CEL. The fix was to replace both of the sensors and to reflash the CPU to the tune of over $600.00! I had to have it done on one of my Pathfinders when I got the CEL at 45k - I was obviously pissed because had I known about the software fix I would have had that done for $50.00 prior to the 02's being damaged ... plus they replaced both sensors. This is one of those things that Nissan should have fixed for free when you brought they car in for service at the dealer -- the software upgrade. The sensor replacement also fell outside of the federal emission warranty because it was for the heater on the sensor and not the sensor portion of the 02. When I bought my second Pathfinder used with 50k on it -- I had the software upgrade done once I found out it was never fixed.

The 02 failure cycle is more than one -- so you may have to drive it a few times before the CEL comes back ......... The only fix is to replace the sensors. I never use the universal sensors -- lots of problems .... also the leads are very long for the rears on the Pathfinders so you need to get the ones that are labeled "exact fit" The sensors are attached to the pipes under the seats just in front of the oval cans that split -- everybody thinks these pipes are catalytic converters -- but they are not.. Make sure to check the pipes to see if they are split/ cracked ........ cheaper to address at the same time.


Sorry to hear about the leaks -- was the pan ever removed for any reason?? Did you start to use a different....... thinner oil or switch to synthetic? I got a RMS leak on the high mile 02 pathfinder when I switched to Mobil 1 - I went back to regular.

[Towncivilian]

The owner's manual recommends at least 91 octane fuel.

Thanks for the information, guys! I did find the TSB for that O2 sensor-related software upgrade earlier. I don't know if mine has had that performed yet - would it be necessary to do if I end up replacing a rear O2 sensor?

[yeldogt]

I have never actually read the TSB -- so I don't know what driving parameters exacerbate the problem -- or if the TSB even addresses this aspect of the failure. Where did you get the TSB? I figured I wold have the reflash done since I had the others fail and the O2 sensors in the used Pathfinder were original.

The heaters bring the sensors up to something like 500 plus degrees -- so they really get hot. The early ones failed often -- my bet is that current sensors have more robust heaters than those built in 2001. So getting this done with new sensors may not be needed .......and if yours are original ....... they lasted this long!

I believe that the manual suggests premium fuel for maximum power -- I use regular and have used regular in both of mine with no issues -- the one has over 140k on it. I had an interesting conversation with a Porsche engineer who told me that you can use regular fuel in all new Porsche vehicles as the controls will adjust for the lower octane -- but you will not get the same power. They have to design the car for many markets and fuel is different all over the world. Now -- this obviously is 2012 and not 2001.

[ARKQX33V6]

Good read!

[Towncivilian]

P0158 popped back up today.

I did have the oil pan gaskets remade with new RTV sealant - I've read that some RTV does not play nice with O2 sensors. Although, how an oil pan gasket could affect an exhaust component is beyond me. Is there any possible relation?

[WPGQX4]

I know that if you don't service your oil regularly that it will affect anything down the exhaust line. The dirtier the engine the dirtier the the combustion, the dirtier the exhaust. Gaskets effecting the exhaust is nothing Ive heard of before

[Towncivilian]

I just finished replacing the O2 sensor. It came out pretty easy with the help of a light hammer tap, no PB Blaster needed. The hard part was removing all the clips that secure the wiring harness - there were five of them. Three were in the engine bay and not too difficult to rip out, but two of them were between the transmission bell housing and ... some other large immovable item in the way, which didn't give me much room to fit wire cutters into to snip the clip. I ended up cutting the wiring harness of the old O2 sensor near the connector in the engine bay to remove it easily. The new O2 sensor had some grey anti-seize applied already, so that's what I used. My 1/2" drive torque wrench's head was too large to work around said immovable item in the way, so I had to settle for using the 1/4" drive torque wrench which goes up to 200 inch pounds (~17 ft pounds), but the torque spec is 30 to 44 ft lbs. I'll have to see if I can get it torqued at a shop tomorrow. All in all it took somewhere around 2 hours but my buddy and I started this when it was already dark - I guess we just like to challenge ourselves. I haven't driven the vehicle yet, but starting the engine and revving a bit didn't result in a CEL so far, and I don't hear any exhaust leaks.

I used a Bosch OE-style sensor (part # 13651) which I got from AAP for $53 after discount code and tax.

[ARKQX33V6]

Towncivilian, make life a bit easier on yourself, next time.
Cut the leads to the sensors at the plugs, cut the old plug out and tie in a new sensor on the old wires and pull through, cutting clips if need be. Do not reclip simply glue the wires in place with regular RTV. Let firm up and dry.

Remove old sensors, put in new sensors then use existing wires as a lead in to pull the new conductors in.

O2 sensors have a definite life, but wait at least 3x to see if the same or surrounding codes cause similar problems.

Good luck.

[ltsnotme]

I sure hope so. A bad O2 sensor would sure be an annoyance after getting my oil pan seals and rear main seal replaced to the tune of $1600... a rear O2 sensor is around $150. But if the sensor ends up bad, I can ignore it for a while since there are no emission regulations in Florida, and as I mentioned, the upstream O2 sensor is the important one. My mother's '07 Altima has had a bad rear O2 sensor for 10k+ miles with no ill effects thus far.

How did it cost so much to replace the RMS and oil pan seal? AutoMD gives an estimate of about $340 to replace the RMS and about $300 to replace the oil pan seal. Have you had it done at a dealership or a private mechanic?

[Towncivilian]

I sure hope so. A bad O2 sensor would sure be an annoyance after getting my oil pan seals and rear main seal replaced to the tune of $1600... a rear O2 sensor is around $150. But if the sensor ends up bad, I can ignore it for a while since there are no emission regulations in Florida, and as I mentioned, the upstream O2 sensor is the important one. My mother's '07 Altima has had a bad rear O2 sensor for 10k+ miles with no ill effects thus far.

How did it cost so much to replace the RMS and oil pan seal? AutoMD gives an estimate of about $340 to replace the RMS and about $300 to replace the oil pan seal. Have you had it done at a dealership or a private mechanic?

For your 3.3L, those prices seem correct.

I had the work done at AAMCO. Replacing the RMS was $1,169.30, and the oil pan seals was another like $400 I think. You can see pictures of my old RMS here.

[ltsnotme]

How did it cost so much to replace the RMS and oil pan seal? AutoMD gives an estimate of about $340 to replace the RMS and about $300 to replace the oil pan seal. Have you had it done at a dealership or a private mechanic?

For your 3.3L, those prices seem correct.

I had the work done at AAMCO. Replacing the RMS was $1,169.30, and the oil pan seals was another like $400 I think. You can see pictures of my old RMS here.

Well, no, I was actually checking prices for a friend's '09 mercedes because she was quoted $1800, and AutoMD still gives an estimate of about $350 ($400 in florida). Same for 2001 pathfinder. Weird.

[Towncivilian]

I found TSB #NTB02-006, 2001 PATHFINDER; MIL ‘ON’ WITH REAR OXYGEN SENSOR DTC PO138-P0140 OR P0158-P0160 STORED. In it, it states that if a 2001 Pathfinder rolls into the dealer with any of those codes, replace the O2 sensor then reprogram the ECM if it falls under a specific ECM P/N. Download the TSB.

My ECM has never been reprogrammed. I have no idea what my current ECM P/N is - the TSB says to use CONSULT-II to check, but obviously I don't have access to one. Should I ask my service adviser about this TSB? They'd probably charge me just for checking my P/N, and since I replaced the O2 sensor myself they might have an issue with not seeing the P0158 and P0159 codes before reprogramming if my ECM is "affected". The TSB doesn't say why it's necessary to reprogram the ECM.

[Towncivilian]

I spoke with my service adviser today and he spoke with a technician about this TSB. The tech stated that if the code didn't reappear within 100 miles or so with the new O2 sensor, reprogramming the ECU isn't necessary. It makes sense though if the dealer is performing the replacement to update the ECU (if affected) anyway to avoid a return/complaint customer.