Rep Power: 0

In the summer of 2017, the Check Engine light came on on my '04 Civic. I hooked up my scanner; it said P0139 - Slow response, Rear O2 sensor (the one AFTER the Catalytic Converter). I replaced it with a Denso sensor from Rock Auto. It lasted for about 2 years, then the same code started firing in July 2019. I replaced it again, this time with a Bosch sensor from Autozone. This sensor lasted 2 months, then the same code came back.

My question is: Am I just buying the wrong sensors? I've heard conflicting stories about wide-band versus narrow-band. Both sensors ran about $60.

Could something else be causing the sensors to fail so quickly? Is it possible a failing Catalytic Converter could foul up the sensor somehow? If so, How could I test that?

 
Rep Power: 222

Well the Bosch is definitely the wrong one

 
Rep Power: 0

If it failed so quickly in isolation, I would tend to concur. However, the fact that the previous replacement failed after just 2 years leaves me a tad suspicious that there may be some deeper problem afoot.

 
Rep Power: 119

Downstream sensor is O2 sensor on all 7th gens, upstream was 02 on most 2001-2003, and then switched to wideband A/F for 04-05.

Lots questions follow.
Is the car “consuming” oil? What type of oil and any additives are you using? High level ethanol in your gas pumps? Any fuel additives?

Is the catalytic converter original or a replacement? Are you putting any “anti-seize” products on the sensor threads?

 
Rep Power: 0

Lots of answers:

I keep pretty good tabs on the oil level, I'm not burning or otherwise loosing much if any (like maybe a millimeter down on the dipstick between 5,000 mile changes?)
I'm using Valvoline High mileage synthetic blend.
I'm pretty sure all western NY gas pumps use 10% ethanol.
I put a bottle of Fuel Injector cleaner into my gas tank after putting in the second sensor (probably about 1 month into its life). Can that possibly cause damage to an O2 sensor?
The cat converter is original.
I have not used anything on the threads.

Thanks!

 
Rep Power: 119

http://www.tomco-inc.com/Tech_Tips/tip4.htm

I would just put another Denso in it, if it looks like any those pictures maybe something else is going on.

 
Rep Power: 0

I'm about to replace an air/fuel sensor (D17A1), and was planning on using a little anti-seize. Why did you ask about anti-seize on the threads? Should I refrain from such things?

 
Rep Power: 222

If you don't know what you're doing you'll put way too much antiseize on the sensor and contaminate it