02 code 2c77 = bank 1 sensor 2 no activity detected
 

Hello All,

Second try at my first post, sorry if the other post pops up.

I have a 2010 E61 with 120,000 miles. Per the vin it was built in March 2010, the last month of production. I recently completed a project that replaced the turbos, the turbo oil and coolant lines, the oil pan gasket, the transmission pan and fluid, various coolant lines, some of the vacuum lines, and all the fluids in the differentials and transfer case. The car is performing significantly better than before I started the project with the exception of the code mentioned in the title. I've been trying to figure this out for about 3 weeks now.

The studs connecting the down pipes to the exhaust tubes were no longer serviceable. Unfortunately, the studs don't appear to have a part number and the local dealer was unable to find an option other than new down pipes. So I took the down pipes to a local repair shop, that heated and pounded out the studs. The pipes are now connected using standard bolts and nuts. When removing the down pipes, I chose not to remove the 02 sensors, partially because I couldn't break them free, and partially because I couldn't see the reason to do so. So perhaps this sensor sustained some none visible damage during this process.

The code was obtained using a Foxwell scanner with the BMW software option. The code description is from my Bentley manual. The Foxwell scanner has the same location, but just the word signal as the description. The scanner shows a functioning sensor when I use the live test function with the engine running. Using the compare function with Bank 1 Sensor 1 and Bank 1 Sensor 2, the graph's move together as the rpm is changed. After clearing the code, the code does not immediately return. It will show up on the return part of the daily commute for example but not on morning drive. I've driven it hundreds of miles after clearing the code without it coming on. Yesterday, starting with a cleared code and a hot car, I drove 20-30 miles with 6 or so stops and engine restarts without the code coming on. I'm guessing that if the engine is hot, the code will stay off.

All four of the o2 sensors were replaced by the local dealer at 105,000 in April 2019.

So far I've:
1) Cleaned and reconnected the sensor to the body harness.
2) Checked for loose wires in the DME. However the wire colors in my car don't seem to match the Bentley manual colors, so I'm not sure I was focused on the right wires.

As mentioned above, the scanner seems to say that the sensor is in fact working and seems to have worked yesterday afternoon.

Anyone had a similar issue? My search of the various forums has not matched what I'm seeing.

Any suggestions are welcome.

Thanks!

Could be an intermittent sensor or something is dirty. Do you always use premium gasoline?

Yes, I always use premium. A dirty sensor is an idea, though. Today, I did a scan after driving around and discovered that the code had been set, but the engine symbol had not illuminated despite multiple starts. All the starts were with the engine warm however.

If the CEL isn't on, I wouldn't worry about it. My car throws codes and my mechanic simply clears them. Codes typically come and go all the time. I think it logs them for historical reasons just in case it gets worse.