Hi guys, I recently had a header replaced (back to OEM), but I am having some trouble with the O2 sensor. There is no CEL (I even cleared the ECU a couple days ago to see if it would come on), however, the cat will not pass smog because of an OBD II code from Mode $06:
MID:$01 TID:$87
- O2 Bank 1 Sensor 1
Test incomplete or dependant test failed

My understanding is that if the sensor is bad, I should have a CEL and other issues (bad A/F ratio, etc.) but I have none of that. What could cause the sensor to not pass self-diagnosis without triggering a CEL?

Yes, I have driven it since the header swap. Originally did ~100mi including the procedure in the manual to force it to be emissions ready, then I reset the ECU and did the procedure again, nada, still the same code.

 

im guessing it failed because the sensor was not ready. So you need to do more run cycles there is a few threads on here about the run cycles that need to be done to get it to complete faster. Its not about how far its gone its about how many trips.

 

copy and pasted the info from another thread from billman Fastest way:

Start the car cold in the morning, drive around local 5 minutes, shut it off (this will complete a "trip").

Start it back up, take it on the highway and set the cruise at 60 for 3 minutes (this will complete a second "trip", and make two-trip monitors "ready" like the air pump monitor).

Example: if you start the car cold, and drive it 10,000 miles without shutting it off, the two-trip monitors will never run and you will fail inspection It's all about parameters...not miles.

 

Thanks for the info. I've tried that. So far, ballpark:
~80 miles of highway
-20 mins at 60mph with cruise
-30 mins at 50-60mph without cruise (as per manual)
-more miles of regular driving (for me, 75-85mph no cruise)
​​​​​​~2h of city driving.
~10+ cold starts
~5+ warm starts

Below is the manual's procedure, which I've followed twice (once before and once after resetting the ECU a couple days ago).

 

Does your CEL light up a few seconds when you flip the key to "run"?

If yes...

There's nothing wrong with your sensor. Stop re-setting the light.

The ECU needs time to ready all the sensors. Drive it normally for a few days.

 

I drove normally (and did the manual's procedure) for a week. Only reason I reset the ECU was because I was doing some other work and thought it might be worth a shot. Even the manual says if that procedure doesn't work there's probably something wrong. I did the procedure plus drove/waited for a whole week before resetting anything.

As for the dash, I cannot recall, but I will take a picture and check later today.

 

No flashing on the dash. Pretty much the same as this video. CEL and gear light come on when put in on but the latter turns off within 2 seconds and the former within 15s.

https://youtu.be/l5zWoCX7prw

 

So your CEL turns on for a few seconds when you flip the key to the run position.

So...your CEL works.

The sensor itself is just a sensor. It doesn't need time to learn anything.

The ECU sees the sensor. The ECU has decided that the system has not been active for long enough to reliably say it's good.

If there is an issue, it lies with the ECU. Not the sensor.

Do you need to get the emissions test done or something? Why does it matter if the ECU hasn't decided everything is ready? Does the car drive differently?

I would just go on living my life. Check back in a few weeks to see if it has all initialized, if you're curious.

 

Yes, I need to get emissions done asap. Aside from that, the manual says if those steps don't fix it, see a dealer, which makes me think it really should be working.

 

Do you have any mods or a tune or anything?