Questions about O2 sensor replacement

[hofffam]

My NSX threw a P0141 code last week - Bank 1 Sensor 2. I know there are a number of threads on this topic. But I couldn't find clear answers to the questions below:

1. Should I replace both rear O2 sensors even if only one failed? The car has 71K miles on it.
2. I am confused about the generic NGK O2 sensors (~$50) vs. the exact replacement. What is different about these? Does it have the correct connector? I see comments about cutting off the original connector and splicing the wires. Isn't that area subject to high heat?
3. When the sensors fail, what is the impact to the engine?

Thanks in advance.

 

[JD Cross]

For the small difference in cost between OEM or generic O2 sensors I went with OEM type from SoS.
The connectors fit so no splicing needed.
I replaced both in case the signal strength from the original sensor was different than a replacement.
The biggest issue I had was getting the old ones out.
My understanding is the O2 sensor provides feedback to the fuel management system so the injectors spray the right amount of fuel.

 

[J KRIB]

Just replace the one defective secondary O2 sensor, the secondary O2 sensors are really only used to monitor catalytic convertor condition and do not play a factor on how much fuel the PCM is going to inject.

 

[davidf]

I somewhat agree here but the car has 2 primary 02's so as a maintanace nut here, I'd opt for both primary's if money allows. I actually have 2 new OEM put aside for when that dreaded light comes on.

Just replace the one defective secondary O2 sensor, the secondary O2 sensors are really only used to monitor catalytic convertor condition and do not play a factor on how much fuel the PCM is going to inject.

 

[J KRIB]

I somewhat agree here but the car has 2 primary 02's so as a maintanace nut here, I'd opt for both primary's if money allows. I actually have 2 new OEM put aside for when that dreaded light comes on.

I would agree with replacing the Primary O2 sensors as a pair if funds permit it but I think he mentioned they were secondary O2 sensor codes. That is why I said just replace the single faultly secondary O2 sensor since it will not affect fuel trim.

 

[hofffam]

Each bank of the V6 has two O2 sensors, correct? The primary and secondary. The P0141 says the secondary one failed for the rear bank of the V6. So my question was whether or not I should replace the same sensor for the other bank. It seems I have a 50/50 split decision.

 

[JD Cross]

I didn't read your comment correctly and assumed that you only had two sensors like my 91.
I have no idea on the importance of the secondary sensors so I should not have commented, sorry.

 

[ftuhy]

Note that P0141 indicates the heater part of the device, not the actual O2 sensing element failed. The heater gets the sensing element up to operating temperature faster, significantly shortening the warm-up period of the control system (but not the mechanical engine parts, of course). This failure is a known weakness with the OEM sensors.

All that said, with this being the secondary sensor, I agree with only replacing the failed unit.
I'd also go with the NSX-specific replacement, rather than the generic. While the actual sensor is the same, the generic one requires you to save the connector and pigtail wiring from the orignal and splice it to the new generic unit. Splices are just another opportunity for a bad connection and decreased reliability. The NSX-specific replacement comes with the correct connector and correct length wiring.

 

[robbiedawg]

i had this same code, PO141,and went ahead and replaced the other sensor on the same bank at the same time.i was glad i did because the mechanic said that when he cleared the code out after replacing the sensor that we knew had failed,there was a second code behind it for that other o2 sensor having failed.

i'm not saying everyone should do this,it may have been a fluke,just passing on what happened.

 

[davidf]

I would agree with replacing the Primary O2 sensors as a pair if funds permit it but I think he mentioned they were secondary O2 sensor codes. That is why I said just replace the single faultly secondary O2 sensor since it will not affect fuel trim.

Sorry, I read it wrong. :redface:

 

[hofffam]

Gonna add to this since I replaced both downstream or secondary sensors yesterday. I bought replacements from SOS - so they were supposed to be plug and play. For my 97 NSX, SOS shipped me the NTK 24061 and NTK 24172 sensors. No indication of which is which (front or rear bank). Sparkplugs.com says the 24061 is the rear sensor, and sells a different one for the front. So it is at least midly interesting that SOS sells a different part.

What I found interesting under the car is that the sensors in my NSX were reversed. What should have been the rear sensor was installed in the front bank and vice versa. I discovered this by removing the rear sensor first, then matching it by appearance to the sensors SOS sent. It matched the 24172. The 24172 has a "male" connector. The connector I made available by removing the rear sensors had a male connector. So the 24172 would not fit. I removed the front bank sensor and found it had a "female" connector. The chassis connectors are not the same to prevent the wrong sensor being connected to it.

A few years ago my NSX had a TSB service from Acura related to emissions control. That service replaced plugs, and all the O2 sensors, among other things.

So the conclusion (after verifying the 24061 connector) was that the Acura dealer intalled the O2 sensors in the wrong locations after the cats. I never noticed any engine issues at all during this time. But I installed the 24061 in the rear bank spot and the 24172 in the front bank spot.

The old sensors came out easily. I used a quick spray of PB Blaster, waited a few minutes. Used an O2 sensor socket with a breaker bar, but didn't need a lot of force. The connectors were a bit difficult to separate, but there is no way splicing wires would be easier. The 24172 was almost an exact match to the Honda part that was on the car - though the rubber bushings on the cable were further apart than factory. The 24061 had a rubber bushing in an unusable location. And it had extraneous clips that didn't mate to anything on the car. I pinned it to the cable bracket using a wire tie.

Reset the CEL with my Android phone and the Torque app. Car runs great.