2000 I30 code P0138 - Oxygen Sensor

[snj2000]

I had my code read at auto zone, they tell me P0138 is an Oxygen sensor - Bank 1 Sensor 2.

I have previously replaced my starter and ignition coils (to give you an idea of my experience level)

So here are my questions:
1) Is the O2 sensor something I ought to be able to replace myself?
2) Any tips or tricks?
3) How can I best find/ identify - Where these sensors are located and which is Bank 1 Sensor 2?
4) I read another post that mentions ECM Reprogramming by the dealer? Is that needed after I replace the sensor? Is that different from resetting the code? If needed and is only done by the dealer, do they usually charge for this out of warranty?
5) Should I replace only this one if that is the only code?
6) AutoZone says I need Rear. Downstream sensor (located after catalytic converter) part 13374 - OEM exact fit which is twice as much as: 15727 ($60 less) - universal. Opinion:
a) how hard it is to adapt the universal
b) recommended one over the other?

Hope that isn't asking too many questions, any input is appreciated.

[yangs13]

heres what i did....maybe itll give you a start.

post4981561.html?hilit=maxima%20codes%2 ... r#p4981561

[loystock]

I had my code read at auto zone, they tell me P0138 is an Oxygen sensor - Bank 1 Sensor 2.

I have previously replaced my starter and ignition coils (to give you an idea of my experience level)

So here are my questions:
1) Is the O2 sensor something I ought to be able to replace myself? - Yes
2) Any tips or tricks? - Spray WD-40 or PB Blaster before sensor removal. An O2 sensor adapter (@ $10 from Amazon) will help.
3) How can I best find/ identify - Where these sensors are located and which is Bank 1 Sensor 2? - Bank 1 is for cylinders 1-3-5 near firewall while Bank 2 is for cylinders 2-4-6 near radiator. Refer to the description below for additional info
4) I read another post that mentions ECM Reprogramming by the dealer? Is that needed after I replace the sensor? Is that different from resetting the code? If needed and is only done by the dealer, do they usually charge for this out of warranty? - No need
5) Should I replace only this one if that is the only code? - Yes
6) AutoZone says I need Rear. Downstream sensor (located after catalytic converter) part 13374 - OEM exact fit which is twice as much as: 15727 ($60 less) - universal. Opinion: - You have to understand that a lot of people don't know the layout of 2000 I30/Maxima exhaust system. You have two Pre-Cats with two O2 sensors each (Front & Rear, a total of 4 O2 sensors )and one Main Cat with no downstream sensor (unlike 98 I30/Maxima or earlier models which have only 3 O2 sensors)
a) how hard it is to adapt the universal - if you understand wiring diagram, have a good stripper and crimper, it should not be a problem. But cutting the wire short and making the wrong crimp-connections may require you to buy another universal sensor. Also, a bad crimp can have poor electrical connection and/or corrosion over time.
b) recommended one over the other? If I were you, I would buy NGK/NTK exact fit. You need P/N: 24574 (HO2S2-B1) and currently is @ $52 at Amazon with free shipping - http://www.amazon.com/s/ref=nb_sb_noss? ... 74&x=0&y=0 . Very hard to beat that price.

I do respect the opinion of 'yang" and hes done great contribution to the forum. But having an O2 extender means cheating the emission system. With the O2 sensor moved away from the exhaust stream, the ECU thinks you're running richer than normal (High voltage) and thus reduces fuel-air ratio resulting in a lean mixture. A lean mixture may save you some gas but will generate more NOx, a pollutant (since there is not enough fuel to consume the Oxygen in the combustion chamber) and result to higher engine temperature. Also, it's possible to fail Smog Check with high level of NOx at the exhaust. I'm from CA so I'm really concerned about pollution.


Here is an info I posted some time ago.
Since owners of earlier I30/I35/Maximas (1999-CA, 2000-CA & Federal and beyond) have started replacing O2 sensors, I think it would help you if I clarify some points about the VQ engine exhaust system and related O2 sensors. Please refer to the diagram posted by "maxhopper" earlier. Unless mechanics know your car, they would inadvertently replace the wrong sensor as what happened to "snookhums."

First, the transverse mounting of the VQ engine places Bank 1 (cylinders 1-3-5) close to the firewall while Bank 2 (cylinders 2-4-6) is close to the radiator. So if you are under the car, the front exhaust pipe is for Bank 2 and merges with Bank1 exhaust pipe downstream of Bank-1 Pre-Cat (This is where some mechanics may get confused).

Front O2 sensor in general is mounted before (upstream) the catalytic converter while the Rear O2 sensor is mounted after (downstream) of the catalytic converter. As applied to VQ engine, FRONT O2 sensor has 3-wire (power, signal and ground) while REAR O2 sensor had 4-wire (power, signal, ground + dedicated signal ground).

On this particular generation of cars, there are 3 catalytic converters - Bank 2 Pre-Cat (in front of engine) mounted vertically, Bank 1 Pre-Cat (below the engine) mounted horizontally and then the main/rear catalytic converter.

As for the O2 sensor location, cable length, original harness color-coding and connector location, see info below:

Bank 1 O2 Sensors
-HO2S1-B1: Front 3-wire sensor with BLACK harness, @ 25" long with sensor mounted on the vertical section of the Bank 1 exhaust pipe with connector mounted on top of the engine, rear pax side
-HO2S2-B1: Rear 4-wire sensor with WHITE harness, @ 38" long with sensor mounted in front of Bank 1 Pre-Cat and connector mounted on the radiator side

Bank 2 O2 Sensors
-HO2S1-B2: Front 3-wire sensor with BLUE harness, @ 11" long with sensor mounted before B2 Pre-Cat (sensor is visible in front of engine) and connector mounted on the radiator side
-HO2S2-B2: Rear 4-wire sensor with RED harness, @ 31" long with sensor mounted downstream of B2 Pre-Cat (horizontal section of the pipe) and connector mounted on the radiator side

For most OEM parts, best pricing is from one of NICO sponsors, IoS (Infiniti of Scottsdale) at "infinitipartsUSA.com a.k.a. "everythinginfiniti.com" also "everything nissan.com. They typically have 25% off MSRP.

For best pricing of OEM and quality replacement O2 sensors and spark plugs, it's very hard to beat NGK.com a.k.a. "sparkplugs.com." This is where I usually buy those particular parts. The "oxygensensors.com" referred to by OP is also reputable and in addition to quality replacement parts, also sells Walker and Universal sensors (requires cutting and splicing of wires). If you are patient enough, you can look at eBay (be wary of cheap sensors) and Amazon.com.

Hope that isn't asking too many questions, any input is appreciated.

[snj2000]

Thanks for the quick replies!

I read Yangs13 post and the referenced post on the extender and my head almost exploded! I too respect what he had done (is doing) but I don't think it is for me

I am going to replace the sensor and have another question LOYSTOCK if you don't mind:

What is the "O2 sensor adapter (@ $10 from Amazon)" - I searched but didn't find a clear result. I don't mind the extra $10 but want to make sure I am ordering what you are suggesting and have a basic understanding of why that is recommended.


Thanks!

[NutriaforBreakfast]

My wifes 1998 Maxima car threw this code 2 weeks ago. I cleared it and it hasnt come back. If the code comes back in a reasonable time, then I will replace the part. Otherwise I will leave it alone.

[NutriaforBreakfast]

I think the sensor adapter is a special socket/tool to remove and install the O2 sensor. Its design will keep the wires from being crushed during the activity (I think there is a hole in the metal allowing the wires
to stick out-kind of like a deep socket with a hole in the side of it). You can probably find at most auto
parts stores.

[snj2000]

Thanks Nutria - I will check the parts store for that socket, I have seen them in my research.

I should have mentioned, I absolutly plan to clear the code and see if it comes back. I did that for my ignition coils, thought I had it beat, but then that code did come back so I replaced them. I was tempted to research whitch coil was bad but most said once one goes, they all will....don't know if that is true but I have over 80,000 on this 2000 and don't plan to get rid of it anytime soon so I was ok with that. (Bit off topic).

[loystock]

'Nutria' is correct about O2 sensor adapter description. It is recommended whenever replacing O2 sensor to protect the wiring from damage. However, for the HO2S2-B1 (Heated Oxygen Sensor 2/Rear-Bank 1) you may not even need it as a good-quality open wrench (not adjustable) will do. That sensor is readily accessible once the car has been jacked up safely.

After reset, if the code comes back again, you have to replace it. A failing O2 sensor usually generates a low voltage (lean mixture) causing the ECU to 'enrich' the fuel-air ratio. Running the car 'rich' for extended period may eventually foul up the other O2 sensors and catalytic converters, aside from higher gas consumption and HC pollution.

As for the O2 sensor from Amazon, the price has now gone up to $72 in just over a day. You may have to check other sites for discounted pricing, if you need it.

[snj2000]

I think Amazon went up because I bought one leaving only one more. I decided for $50 to just do it. It won't be here until next week, so hopefully I won't muck up anything by putting on a couple hundred miles since the engine light came on.

I looked under the hood but couldn't locate the o2 sensor. I understand it to be firewall / passenger side. I have seen what they look like but not the specific location on my engine.

When you said: "That sensor is readily accessible once the car has been jacked up safely."

I guess that means I will access it UNDER the car? I have a jack & jack stands so I guess I will search underneath next.

[NutriaforBreakfast]

The sensors themselves are under the car. There will be a wire trail to
connections under the hood (which further connect to the computer/ECM)
I think

[loystock]

[quote="

When you said: "That sensor is readily accessible once the car has been jacked up safely."

I guess that means I will access it UNDER the car? I have a jack & jack stands so I guess I will search underneath next.[/quote]

Bank 1 Pre-Cat is mounted horizontally, below the engine, pax side. The Front sensor (HO2S1-B1) is mounted on the vertical pipe while the one you would like to replace, Rear sensor (HO2S2-B1) is mounted in front of the Pre-Cat, with a White harness (if original) and a 4-pin connector near the radiator.

[yangs13]

i had an in depth conversation with a fella who owned a '01 max, a man who i trust (he built a conquest with a 2jz in it) with automotive knowledge. i was told the codes would not go away, even if i change the cats, o2's, maf, etc...and something else about reflashing the ecu. it was cheap and seemed like a sensible fix for me at time; i was in school (i.e. no money).

[loystock]

Yang, I hope you were not offended about my comment on the O2 sensor extender.

Sometimes, you have to make do with the available resources. One time, I have to replace a starter in my daughter's car inside a school parking lot. Way back in the early 80s, the clutch cable in my first car (78 Galant) broke. I have to use regular wire to operate the clutch, limped back home, then got it replaced.

[drivewaydan]

Trying to get the same sensor from a local Autopart store - So is this sensor considered to be on the Pass. side? I know it is the rear sensor but the listing is showing driver or pass side.

[loystock]

There is a likelihood that your local parts store is using an older data base. The 99 and older I30s (except 99 I30 with CA- Emission) have 3 O2 sensors - 1 for left bank (Bank 2), one for Right Bank (Bank 1) and one downstream of the main 'cat' (Rear O2 sensor). The 2000 and newer I30s have 4 O2 sensors and the description is already in my first response in this thread. You'd be better off ordering the part from NGK.com or from Amazon.com. The part number is also in the posting, assuming that you have the same trouble code.

[snj2000]

Loystock, thanks for the GREAT information! I replaced the O2 sensor today and your description of the location of the sensor and connector and harness color were dead on and made the process so much easier for me. The whole process took under 2 hours, probably a quarter of that was raising the car and securing it on the jack stands. Being that I was going to be under it and cranking on the sensor to break it loose, I obviously wanted to make sure it was stable. Was about 95 degrees in the driveway this morning with high humidity but I guess that beats rain or snow!

I still need to reset the code, I don't have a code reader. Every time I get the SES light, I plan to get a reader, then I finish the repair and never think about it again untill I get another light

My daughter took it out for the afternoon. I am not sure if it will detect the correct voltage and turn out the Service Engine light or more likely I will have to pull the battery ground over night.

$50 for the part and a few hours work vs. perhaps $300.00 or more at the dealer......if the SES light gets reset & doesn't come back, then it was a good day!

[loystock]

I bought my scanner some time ago. One of the best investments I've ever made. HarborFreight has a scanner from Cen-Tech that can display live O2 signal and read PCM data stream for @ $120.

[snj2000]

After replacing my o2 sensor, the Check Engine light went out the same day!

After about 10 days, the check engine light came back on

But I bought a code reader and now I have a P0420.

Do you think that means I need to have me ECU reprogrammed?

This is a 2000 I30 with >80,000 miles.

If it needs the ECU reprogramed can only the dealer do that and about how much should I expect to have to pay for that?

Thanks!

Joel

[loystock]

For this new trouble code, we have to dig deeper into the vehicle history. I always advise club members not to ignore the CEL as it could lead to more expensive repair in the future.

So how long have you had this bad O2 sensor before you decided to replace it? A bad O2 sensor usually causes the ECU to give a richer fuel-air mixture, which not only increases gas consumption but over an extended period may damage the other O2 sensors and the catalytic converters.

I strongly recommend that you clean the MAF sensor (CRC MAF Sensor Cleaner, @ $8 from Autozone) and replace the air filter, if dirty. Also clean the Throttle Body (use a rag, never spray carb cleaner directly into the assembly). We would like to eliminate other possible causes as the repair for this problem may be expensive.

The Catalytic Converters (2 Pre-Cats and 1 Main Cat) or 3-way catalysts oxidizes the HC (hydrocarbons) into less harmful H2O (water )and CO2 (carbon dioxide) and the CO (carbon monoxide) into CO2 and reduces NOx (nitrous oxide) into N2 (nitrogen) and O2 (oxygen). This is made possible by precious metals inside the cat - platinum and palladium for the oxidation and platinum and rhodium for the reduction. Aside from that, a good 'cat' can STORE OXYGEN.

Once the engine is warm (closed loop mode), the O2 sensor looks at the level of Oxygen at the exhaust to measure combustion efficiency. It generates 0-1 VDC with an ideal voltage of 0.45-0.50 VDC (Stoichiometric ratio of 14.7:1) with Lean Mixture (high O2 level) of <0.3VDC and Rich Mixture (low level of O2) of >0.8VDC. This signal is processed by the ECU to adjust the fuel-air mixture accordingly. The result would be switching (transitions) RICH-LEAN-RICH and so on.

With the above in mind, the Front O2 sensor sees the actual level of O2 (high switch rate) while the Rear O2 sensor, due to O2 storage capability of the cat, will have less switch rate. If the cat is bad, then it can no longer store O2, so the switch rate of the Rear O2 sensor approaches the level of the Front O2 sensor. When this happens, that code (420 for Bank 1 and 430 for Bank 2) is generated. I cant remember exactly but I think you normally have 5-7 transitions in 10 seconds for the front and 2-3 for the rear.

So most likely, you have a bad Bank 1 Pre-Cat. But that is an expensive component, OEM in particular. So you would like to CHECK if you have exhaust leak, bad fuel injectors or ignition issues before replacing the cat.

You have several options - replace the front sensor and hope that it fixes the problem; use the rear O2 extender recommended by another forum member (but may be harmful to the environment and your car); or replace the Bank 1 Pre-Cat, assuming you have eliminated other probable causes - exhaust leaks, injectors, etc.

[snj2000]

The original check engine light P0138 was on for about 3 weeks by the time I got the code read, your good advice and the part ordered/ delivered/ installed. I would guess less than 300 miles.


I keep coming back to the re-programming of the ECU (wishful thinking?) because:
a) I see other posts online referring to that.
b) This service bullitin (but I don't know how to tell if mine is on Chart A- Dealer I guess?) - http://ww2.justanswer.com/uploads/badda ... 0-054b.pdf
c) I see the P0420 on my service record from 2003 at 27,000 miles where they reprogrammed the ECM - Not sure if that means, since it was already don't it doesn't need it again?


- I replaced the air filter yesterday, dirty but not terrible.
- I will clean the MAF sensor. (I noticed the air intake was a mess, gaps and some foam weather strips decayed. I reconnected everything and replaced bad foam. Cleaned everything as best I could. This was all on the PRE air filter side. Looks like the MAF will be POST air filter?)
- I will also clean the Throttle Body with a rag. (I guess I will have to remove it?)

I have no problem replaing the front sensor to see if that helps but I may be over my head now because I don't kow how to do any of this....
"CHECK if you have exhaust leak, bad fuel injectors or ignition issues before replacing the cat."


Thanks again for all your help.

[loystock]

Here is my response to another forum member (yesterday).

"If time and money is not an issue. ECU re-programming at the dealership is good as they may have the latest SW upgrade. The cost is @ $100. When the Throttle Body in my 03Q was replaced under warranty, Beshoff Infiniti did not charge a single cent for diagnostic (@ 4 hours), component replacement and ECU SW upgrade. I love Beshoff!!!"

AFAIK, most 're-programming' is just clearing the 'learned' fuel and ignition maps/parameters of the ECU so it returns to default parameters. This you can do by simply disconnecting the battery for 30 mins or more or using the OBD II scanner to RESET the fault/ECU. These parameters are 'learned' by the ECU in the course of your driving over the years as various sensors deteriorate over time and the ECU has to adapt to it. HOWEVER, ECU re-programming may involve SW upgrade (plus HW as needed) to adjust fuel and ignition maps, transmission shifts, etc/ or rectify an internal fault or obsolete SW/firmware. This is when a paid re-programming is WORTH IT. And it may apply in your case as they have done re-programming before to correct a similar problem a while back.

You can take out the entire air intake - from filter box all the way to the throttle body (TB) by unlocking the clips on the filter box, disconnecting the MAF sensor connector (push release tab until it 'clicks' to release), disconnecting (and labeling if you're not familiar) the tubes to air intake and loosening the adjustable clamp to the TB. There may be some clamping bolts/screws that you have to remove to take out the air intake. You can then do your cleaning.

In checking for exhaust leak, look for the obvious like cracks or loose gaskets. But for detailed checks of exhaust, injectors, ignition, etc. it may be beyond your capability and best left to qualified shop personnel.

You can also try a 'creative' reset of the ECU. Disconnect both battery connectors and wait at least 30 mins. This will clear the ECU of 'learned' parameters normally stored in the volatile RAM memory. Then connect the battery connectors together or short them out (DO NOT CONNECT TO THE BATTERY). This will clear (discharge) any stray/residual capacitance inside the ECU. Reconnect the battery connectors, clean as necessary. Drive the car and see if the problem goes away. If it comes back, then you can go to the dealer for re-programming or try to replace the Bank 1 Front O2 sensor first (sensor with black harness on vertical portion of Bank 1 exhaust pipe with connector on the rear engine compartment, pax side) and see if it works.

An O2 sensor has a typical lifetime of 100,000 miles but may be affected by the environment it is subjected to (gas quality, contaminants, leaks, etc). Some people replace them in pairs while others (like me) replace them as failed. As the car owner, it's always your call.

[snj2000]

Um, thanks for the reply "thewitt".

"Loystock" replied 2 months ago with excellent information that put me on to the part I needed and how to replace it. As I noted above on July 25th, I replaced the sensor and hthe check engine ligt went out on its own.

I did get a P0420 code a couple weeks later, also noted above, but again followed some of Loystock's great advice and after resetting that code, I have had smooth sailing for about a month now. (maybe I should have created a new topic for that code?)

Anyway I appreciate all of the great information provided in the forum!

[loystock]

I'm glad the problem has been fixed. And yes, we do appreciate members giving feedback as to whether our suggestions helped or not. It's one way of helping other club members.