Yeah, its HFM. Its actually a 93 300E 2.8, but it doesn't change much. It has the M104 engine.
I already replaced the OVP earlier, and no dice. I just ran outside to check the fuse, and it is still good. The computer _seems_ to have power, because the diagnostic port works, which is wired directly into the ECU. This car is the Federal version, and doesn't have a seperate diagnostic model.
It could be another sensor causing trouble, but logic would have it that the heater for the O2 sensor would still get power, even if the computer was ignoring the readings. Since we've got no power on the O2 heater, and its ignoring the readings, I still think it might be the computer (although I'd LOVE to be proven wrong!)