2002 S60 Rough idle but smooth at higher RPM

[quietcoolone]

I always thought it was the 2003 and 2004 that had the fandangled oil trap. Also I wasn't aware it was in any way connected to intake vacuum.

Great work draser and to you quietcoolone for persistence in this matter.

There is a small elbow hose from intake to oil trap-- (a real pain fitting onto intake).
I'm happy for the help and insight posted on this thread. I can now move on to replacing shocks, tires and mad vibration when in Drive or Reverse at low RPM (goes away when in Park or when put in motion)

[draser]

Gotta help a brother in need... Good challenge.

[draser]

So you basically inserted a LPF - low pass filter - in second O2 circuit and ECU now reads the slower integrated signal, good to know.

[quietcoolone]

So you basically inserted a LPF - low pass filter - in second O2 circuit and ECU now reads the slower integrated signal, good to know.

YES sir!!
There is nothing wrong with the O2 Sensor (computer not happy with reported Voltage/Frequency)
I used the resistor to drop signal voltage from 0.9V to 0.5V and the cap to slows things down to approx 4.7s (in layman terms).
Prior to the mod, the CEL (P0420) would return in as little as 10 miles, after the mod the car has been driven over 100 miles and so far so good.