1993 300E's have the HFM 3.2 liter engine. They are mis-badged. Read my signature below. I don't know why MB didn't call this model a 300 E 3.2 (like they badged the 1993 300 E 2.8), or 320E (like the rest of the world), or even E320 (like 94 and 95).

1993 300E's and 1994-1995 E320's have the same VIN #, engine, and chassis code.

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!)

There is one other possible clue to this puzzle: the computer is also giving me a code 11 on pin 14 of the diag connector. This looks up to be:

-Closed throttle recognition signal to engine control module
-Fuel saftey shut-off to engine control module

Normally I'd say the CTP switch in the throttle actuator is dead, but that ain't the case here. I get this code with a throttle actuator I got from sugnami, and it is still good. So it has to be something else.

I have no idea if this sheds any light on the problem (it didn't for me), but I thought I'd mention it....

My '90 M104 failed last year with pretty much the same high readings. Problem was the thermostat. Engine would not warm up fast enough which causes engine to run rich longer which causes catalytic converter to load up which causes high readings. This can also cause catalytic converter to fail. If you find this to be a problem, it could take up to an hour of driving to lower readings once corrected (need to clear out catalytic converter).