2002 C240 W203 - URGENT NEED HELP! P0140, P0141, P0160, P0161

[DickHertz]

I changed my Downstream O2 Sensors because I initially had P0140 and P0160. But now I have P0140, P0141, P0160, P016. So I reinstalled my two original O2 sensors and reset the codes. Drove the car and now four codes came back when I only had two originally!

I have unplugged the O2 Sensor wiring connector inside the fuse box under hood on drivers side and checked the wires for continuity and resistance going down to the sensor plugs (O2 Sensors Unplugged) and all wires are ok measuring 2-3 Ohms.

When I initially unplugged the O2 sensors and measured the voltage it showed 14VDC. Now that I plugged the sensors back in and checked the voltage fluctuates between 0-6 VDC

I unplugged the O2 sensor wiring connector in fuse box and measured going to the ECU and it shows a fluctuation between 10.6 - 12.8 VDC.

I have cleaned and tightened some of the grounds under the hood (Passenger side was a little loose, but no difference).

I do not think the O2 sensors are bad since a few other electrical gremlins are afoot in this car. Left rear brake light has no power but right side works. Right rear turn signal does not work but side mirror signal and front do work.

I really appreciate any help you could give. I only have a few hairs left after pulling out all the others. Lol

Thanks,

Dick