W124 O2 Sensor Problem
Here is one for the smart minds: Computer tells me there is an O2 sensor problem. Two codes: 'Incorrect voltage from 02 sensor' and 'Heater amps too high/shorted'.
There is _no_ current to the O2 heater, and a continuity check finds an open circuit from pin 7 of the fuel pump relay, where the schematic says the O2 heater is connected. That would lead me to think there is a break in the wire, but that seems _very_ unlikely.
Meanwhile, the 02 sensor itself is reading only 0.1V, even after being heated up by exhaust. Normally I'd say its a bad sensor, but I just replaced it in April and it has less than 10K miles on it. Its an OEM sensor.
Any ideas? Is there a fuse on the heater wire that might have blown? I didn't see anything during 3+ hours of inspection.
The car is a 93 300E.