kskane

Symptom: When I stop at the red light with AC on, the breaths like a athlete. You know when you run a bit and stop and then you breath heavy and deep, it like similar to that. Engine vibrations are not fluctuating much, but I can feel increase in the vibration and then decrease and it goes in a cycle.

I pulled out the following code repeatedly from the car along with oil level sensor gone bad.
29A3 Oxygen sensor before cat. conv., bank 2: signal = P0154

Would the cat converter be responsible for the above behavior or does any one else know what that breathing is all about.

Also on my E60, there are 4 O2 cat sensors, 2 front, 2 back. But strangely, the P/N for all four are different as below;
11787503441 (570mm)
11787518495 (570mm)
11781433940 (990mm)
11787513963 (990mm)

Do while buying, do I need to ensure that I buy 4 separate part numbers or can I 2xFront sensor (either 11787503441 or 11787518495) and 2xBack sensor (either 11787513963 or 11781433940)?

What brand of Sensor are OE and OEM reliable?

Greg_V

You don't mention the year/engine/mileage of your car. I have a 2007 e61 with an N52 engine. I just replaced my O2 sensors at the 120,000 mile service not too long ago as called out in the maintenance intervals.

The O2 sensors help the ECU control the mixture, so a bad sensor could be causing the breathing issue you describe, if I understand it right. (Video/audio would help)

One of the O2 sensors I installed had been damaged during shipment. It threw a different fault but gave a similar symptom of rough/unsteady idle. Once I put in a good sensor, the CEL fault cleared and idle returned to normal.

Yes, the sensors and the connectors were different pre/post cat. I believe the two pre-cat sensors are identical except the cable length. Same with the post-cat sensor pair. At least they were on my N52.

I opted to use NTK sensors and have had no issues. I believe the damaged sensor occurred in shipment due to lack of overpack. BMW/Bosch/NTK cross reference attached, with lengths, for my E61 2007, N52 engine. Don't forget the bolts for the shear plate if you replace the post-cat sensors.

After you take care of the O2 sensor, if you still have problems, you might also check you air/oil separator as well as check for other vacuum leaks. There may be more than one issue causing your symptoms.

Greg_V

BTW, a Google search on BMW P0154 will reveal this thread--http://www.bimmerforums.com/forum/showthread.php?1176270-P0154-O2-sensor-circuit

More specifically, the code means there is no electrical signal coming from the sensor. Could be a connector, wiring, or sensor problem. Good luck with the trouble shooting.

kskane

I checked the connectors, all wires seems to be okay.

I have 2004 E60 with M54 engine, if that helps.