Replaced O2 Sensors still getting Increased Emissions. Pulled Code 2726

[iamthestig_91]

Hey Guys, trying to get my car smog ready and i had Test Pipes before so i was always used to the Increased Emissions warning light but i replaced the entire Cat / front silencer with a stock one i found locally.


Went through a drive cycle and still got an increase emissions light after. Figured it was due to a faulty sensor. So i replaced all 4 Lambda sensors (but a used set) and did not have the check engine/increased emissions light turn on during the drive cycle. Took it to get smogged and it did not pass OBD readiness. Drove it around some more and then i got the error code again. Really lost as to what i need to do.

Pulled codes using INPA just after i got the error and it is attached. Some direction or guidance would be greatly appreciated.

[amrazM]

Pull the live data to see what reading both primary o2s are seeing. an exhaust leak from the donut at the header to midpipe will cause a fault to be present.

[Theodore]

When I had a similar issue that I couldn't track down, it turned out to be a damaged wiring harness to the O2 sensors in my case. BMW Part # 61127842478.

[iamthestig_91]

Theodore amrazM

Thanks guys, I think ill try pulling Live data. If i see that the O2 sensors are spitting out something then the wiring harness is good. Will look into replacing the gasket (#3) in photo from first post. I do remember it being a bit torn, or very loose.

I am also suspicious that the Code was thrown at the exact same mileage as when the coolant temperature rose (See the attached Image in first post). before that, it didnt trigger a trouble code.

[drwankel]

Originally Posted by iamthestig_91

Theodore amrazM

Thanks guys, I think ill try pulling Live data. If i see that the O2 sensors are spitting out something then the wiring harness is good. Will look into replacing the gasket (#3) in photo from first post. I do remember it being a bit torn, or very loose.

I am also suspicious that the Code was thrown at the exact same mileage as when the coolant temperature rose (See the attached Image in first post). before that, it didnt trigger a trouble code.

The gasket should be replaced every time the x pipe is removed. The gasket is soft and compresses quite a bit during installation. It's not an expensive part.

[iamthestig_91]

Originally Posted by drwankel

The gasket should be replaced every time the x pipe is removed. The gasket is soft and compresses quite a bit during installation. It's not an expensive part.

I never said it was expensive. But thanks buddy. Ordering a few.

[omgzirra_exe]

Originally Posted by iamthestig_91

I never said it was expensive. But thanks buddy. Ordering a few.

someone def took this the wrong way and got hurt.

[pbonsalb]

I re-used gaskets several times before replacing. Certainly won’t hurt to replace and if you have unresolved issues, you have to keep trying different things.

I did ruin an 02 by banging on the midpipe once. Remove them before you bang on a pipe they are in. And disconnect them before removing them. Don’t leave them connected and just twist up the cable.

[nurburgracer]

Originally Posted by iamthestig_91

Theodore amrazM

Thanks guys, I think ill try pulling Live data. If i see that the O2 sensors are spitting out something then the wiring harness is good. Will look into replacing the gasket (#3) in photo from first post. I do remember it being a bit torn, or very loose.

I am also suspicious that the Code was thrown at the exact same mileage as when the coolant temperature rose (See the attached Image in first post). before that, it didnt trigger a trouble code.

Did you get this fixed? If not, it seems like the coolant sensor/sensor wiring may be the actual fault.

[iamthestig_91]

Originally Posted by nurburgracer

Did you get this fixed? If not, it seems like the coolant sensor/sensor wiring may be the actual fault.

Didnt get it fixed but i replaced the sensor and the thermostat. Also replaced both donuts at the headers. Cleared codes and was going through a drive cycle only for the "Increased emissions" Error to pop up again.

Pulled codes and got 2727, 2726, and 2776. All thrown at the same mileage. Which leads me to believe that 2776 (DMTL-Pump) is the culprit now.

If this is the wrong approach, please let me know. Really annoyed chasing this issue but at least it is a different issue now than my first post.

[The-Traveler]

Hope you changes pre and post cats. It's a lie that the post cats are just for efficiency, they're not.

[iamthestig_91]

Originally Posted by The-Traveler

Hope you changes pre and post cats. It's a lie that the post cats are just for efficiency, they're not.

I bought a used set of 4 on eBay that said they were working. Not sure if I should just buy a new set now.

[djan9el]

Originally Posted by iamthestig_91

Pulled codes and got 2727, 2726, and 2776. All thrown at the same mileage. Which leads me to believe that 2776 (DMTL-Pump) is the culprit now.

Not sure if this is related to your main issue, but just in case, I used to have a similar "Increased emissions" error message and code 27C3: DMTL leakage detection. Replacing the pump didn't fix the issue. I finally was able to fix the problem by replacing the Fuel Tank Vent Valve (13907838281). Hope it helps.

[pbonsalb]

Originally Posted by The-Traveler

Hope you changes pre and post cats. It's a lie that the post cats are just for efficiency, they're not.

I did not understand this until the last year or two, but apparently ECU of this vintage and newer have some sort of feedback between the front and rear 02. People using rear 02 modifiers have discovered this.

Used 02 may still be good but banging on the pipe they were in, like some salvagers may do, can wreck them. And some people twist the cables to remove them because it is easier than disconnecting the harnesses and that can also damage 02s.

[The-Traveler]

Originally Posted by pbonsalb

I did not understand this until the last year or two, but apparently ECU of this vintage and newer have some sort of feedback between the front and rear 02. People using rear 02 modifiers have discovered this.

Used 02 may still be good but banging on the pipe they were in, like some salvagers may do, can wreck them. And some people twist the cables to remove them because it is easier than disconnecting the harnesses and that can also damage 02s.

Yeah the pre cats are 0-5v and the post cats are 0-1v so one is high res and the other low res. So they calibrate each other.

[nurburgracer]

Originally Posted by iamthestig_91

Didnt get it fixed but i replaced the sensor and the thermostat. Also replaced both donuts at the headers. Cleared codes and was going through a drive cycle only for the "Increased emissions" Error to pop up again.

Pulled codes and got 2727, 2726, and 2776. All thrown at the same mileage. Which leads me to believe that 2776 (DMTL-Pump) is the culprit now.

If this is the wrong approach, please let me know. Really annoyed chasing this issue but at least it is a different issue now than my first post.

Those 2 codes 2727 and 2726 are no longer present. 2776 looks to be your problem. It could be the pump that's faulty. Check the pump wiring too.

[Scrippy]

Originally Posted by drwankel

The gasket should be replaced every time the x pipe is removed. The gasket is soft and compresses quite a bit during installation. It's not an expensive part.

That's not really necessary actually. It depends on the gasket itself. I've reused mine like 4 times. The last time I attempted, I beat up the gasket lining up the joint and yes I had to replace them. Just be careful not to damage and make a judgment based off thickness. If they aren't crushing any thinner when tightening then replace.

[Scrippy]

If you suspect the pump pull the intake hose 1" just after the air filter during a cold start. If there is suction equivalent to a strong shop vac you're probably ok on the pump. If that doesn't suffice then pull the outgoing side off and do the same to feel the air. FYI the pump only comes on for like 10-15 seconds after a cold start (10 hours or so). Our secondary air passages in the heads are getting clogged and can result in weird O2 readings. I have 27B0 which is more direct to this point but I wonder if your blockage is just starting?

[DrFerry]

DTML Pump, Worn Gas Cap seal, or Fuel Tank Breather purge valve (or its connector).