My 2000 4.4i has the check engine light on for last couple of month. I´m in Africa and there´s no BMW assistance. Car has been running great for the last four years (before that it was in Europe and only a gearbox was required, nothing more) with no critical problems apart from the usual.
Few months ago the check engine light went on and I can feel loss of power at 4500rpm, it strugles a bit to rev after 4500rpm.

Manage to arrange a litle machine that can read the ECU and this is what it shows:
- 02 sensor circuit no activity detected
- Bank 1 sensor 2
- System to lean bank 1
- System to lean bank 2

There are several other information about the engine parameters like MAF and others, but only these this faults showed up.