When you get an O2 sensor **HEATER** code, that usually means an open circuit to the O2 sensor. There are 4 wires to the sensor- two get the actual signal, the other two are for a heater to warm up the sensor.

If you reset the code and, on next start IMMEDIATELY get that code return, it is the heater in the sensor OR the connections to the sensor OR the fuse to the heater circuit.

And PHL08- have you looked from underneath? Ive not done it on E70s, so no idea. But I dont think Ive ever done an O2 from above on any car....

Oh, hate to change it to find out it was a fuse or connector loose.