[pyhee]

Hi All,
In short: A bad oxygen sensor before catalyzer on bank 1 has caused me rough idle, misfiring codes and deteriorated the situation into limp mode. I replaced the O2 sensors before cat on both banks, reset adaptation and completely solved the problem.

I have made the DIY work a YouTube video, hoping this will help you guys who have the same issue. Please watch:

***Parts Required***
Oxygen sensorBEFORE CATALYZER X2
BMW 11 78 7 537 984
Bosch LS 17038 / 0 258 017 038

***Tools Required***
8 mm hex socket (trims)
10 mm hex socket (trims)
17 mm hex socket (reinforcement strut/plate bolts)
torque wrench with angle (56 Nm)
22 mm open hex spanner (O2 sensor)
22 mm open hex torque spanner (25-50Nm)

***Work outline***
1. Remove transmission cover
2. Partially release bumper lower trim
3. Remove reinforcement strut/plate
4. Replace O2 sensors before cat
5. Reset adaptation
6. Test run
7. Assembly

***My Symptoms in order of occurrence***

1. Codes about O2 sensor before catalyzer on bank 1
   The car did not have serious sickness at this moment. The code could be cleared and would come back some time after driving. It would not come back right at next start.
   
   Below are the history random codes (they come randomly);
   2724 DME: Oxygen sensor, signal before cat., bank 1
   2726 DME: Oxygen sensor, plausibility before cat., bank 1
   2728 DME: Oxygen sensor, coast-mode diagnosis before cat., bank 1
   2742 DME: Oxygen sensor heater resistance diagnosis before cat. converter, bank 1
   2748 DME: Oxygen sensor before cat., evaluation module in control module, bank 1
   277C DME: Oxygen sensor trim control diagnosis, bank 1
   
   I ignored it because I though it was caused by my exhaust mod. Shame on me.
2. Loss of power at drive-off
   After start, the car seemed didn't want to leave the parking space. Pressing more on the throttle peddle didn't help. But shortly normal driving was possible.
3. Rough idle
   The kicking and knocking of engine became noticeable. And it always occur at idle, no matter the engine was cold or hot. It became an earthquake as days went.
4. Limp mode
   The shaking at idle became so serious that misfiring was all over cyl 1-4 and ONLY on bank 1. There were misfirings with fuel cutoff. The car went into limp mode.
   
   Below are the codes accompanied with limp mode;
   2B35 DME: Misfire with cutoff, cyl. 1
   2B36 DME: Misfire with cutoff, cyl. 2
   2B37 DME: Misfire with cutoff, cyl. 3
   2B38 DME: Misfire with cutoff, cyl. 4
   2B41 DME: Misfire with cutout, several cylinders
   2B42 DME: Misfire impairing exhaust emission, cyl. 1
   2B43 DME: Misfire impairing exhaust emission, cyl. 2
   2B44 DME: Misfire impairing exhaust emission, cyl. 3
   2B45 DME: Misfire impairing exhaust emission, cyl. 4
   2B4E DME: Misfire impairing exhaust emission, several cylinders
   
   Restarting could exit the limp mode but the rough idle will trap the engine again.