Oxygen Sensor - location?
 

2001 Integra LS, B18B1 engine type.
Service manual says the primary oxygen sensor is located in the B exhaust pipe, not the TWC. Acura parts guy says both 02 sensors are on the TWC.
Which is it?
Here's why I ask:
Midas replaced the B exhaust pipe. The MIL came on 2 blocks out of the shop, and they said the code "indicated a problem with the H02S". Geniuses reset the ECM, didn't troubleshoot the problem. The MIL came on again after driving about 5 miles. Of course Midas categorically denies they could have broken the H02S. "It's nowhere near the B pipe."
NEVER go to Midas.
-Al

the oxygen sensor is on the a pipe not the b. the b pipe is the pipe after the cat to the muffler section. midas is right.

Ok, since it's the primary o2 sensor it would be the one closest to the head on the piping. Get under the car and look for yourself.

They probably never plugged it back in. I've had similar experiences with midas.

All points taken, especially the one about getting under the d--- car and looking for myself. Tough to do while parked on a NY city street, though. I'll try to find a parking lot.

Can't say Midas is RIGHT yet. They didn't say it was the primary H02S. Just "the H02S." The secondary is close to the B pipe, no? I hope the suggestion that they just need to plug it back in works.

So I'll quote directly from the service manual to explain my confusion:
"The H02S is installed in TWC housing (B18c1, B18c5 engines) or exhaust pipe B (B18B1 engine)." P 11-67. It must be a typo; makes no sense for the primary to be pre-cat.

Thank you all.

Oops, I meant "makes no sense for the primary (H02S) to be POST-cat."

Sorry.

most of the time the upstream O2 is on the header. however my car has both on the cat. I've never gotten a good explaination for this but I believe the CA-spec integras have the upstream (#1) O2 on the header, however I think most of the integras are CA spec, even many of the ones that were sold outside of CA.

2001 LS

One should be on the "header" pipe near the "tunnel" where you would stick your arm to get the oil filter out.

the secondary o2 sensor should be on tail end (after the catalyst) of the cat.

not on B-pipe.

Took it back to Midas, resolving to get the exact DTC. Midas said it was PO141 (O2 Sensor Heater Circuit Malfunction Bank#1, Sensor#2). And they reiterated that there was No Way replacing the B-pipe could have messed with the secondary HO2S. They showed me the sensor locations while the car was up; secondary looks to be off the rear of the cat, but quite close to where the B-pipe is bolted in. I remain skeptical about the impossibility of doing damage while yanking off the pipe.

Anyway, I'm thinking of going to the dealer to have the heater circuit tested first, hoping it could still be a loose wire, rather than throw $267 + labor at a new sensor.

Oh yeah, Midas also told me the MIL will automatically come on after 50k miles if I don't replace the oxygen sensors, which don't last more than 50k miles. What?

midas is full of sh!t when they speak of that 50k mile stuff.

theres plenty of places online that sell NGK 02 sensors with honda connectors for weellll under 100 dollars. and its easy to change yourself.

stop going to midas and go to a privately owned honda service place.

advance sells a bosch replacement for $80 worked for me.

If they're saying the code is for a bank 1 sensor 2 then it would be the sensor closest to the back of the car after the cat.

That is fucking bullshit about the 50k mile crap. Stop going to Midas and go to the dealer where they actually know what they're talking about and not throwing bullshit at you.

once you change exhaust you should change the both o2s due to the fact they werent reading right with a bad exhaust leak and probably damaged them-figure u had exhaust leak to change the pipe!

Yeah, I'm over it with Midas - just needed them to lift the car and give me the DTC for free so I could see everything for myself. You can't believe the never-ending stream of crap these guys dealt me. Thanks for confirming that the HO2S "death at 50k" line was total BS.

I was wondering about the possibility that the leak in the B-pipe damaged one or both HO2 sensors, as JKAE suggested.

Going to the dealer.


BTW, of you ever have a problem with them, Midas HQ will not do jack to help you with the branch. They give you the line "we can only suggest that the 'area representative' call you" (which is also BS - the individually-owned-and-operated franchises do not report to any corporate regional supervisor; the "area rep" is typically the franchise owner him- or herself). If you don't get satisfaction from the branch where you had the service performed, your only recourse is through the BBB or your state's office of the attorney general. And who wouldn't want to spend several fun-filled hours slogging through that complaint process?