2004 TL, 220k miles. Both cats most likely need replacing soon. Had the pesky P420 and P430 codes. Corrected them with resistor and capacitor hack.
Generally you need a 1 Micro farad cap and 1 megaohm resistor. Polarity of the cap is important; positive of the cap in the signal wire, negative on the other. The cap goes on the Ecu end of the wires, not the sensor end.

However, after installed for testing I got a high voltage code p0138, so it was easy enough to add another 1 megaohm resistor, after the cap across both wires, which smoothed the voltage sine wave and now is a steady 6 volts (within range).
Now CEL is off and no problems.see the attached diagram. I will get the cats done soon enough, so this is just buying me some time to pass the visual on smog test. Do not distrub the two heating circuit wires.

 

why not use an defouler on the secondary sensors to trick the car? seems easier than wiring in the caps/resistors and is easy to put back when you get new cats or go catless.