Since turbocharging my IS300 this summer, I've been plagued with P0420 & P0430 codes -- Catalyst System below Efficiency. I tried simulating the output with my Innovate Wideband MTX-L, but after many months and configurations, I've given up. So I built a simulator based on a 555 Timer IC. I will install the new simulator tonight and report back w/ the results. Hopefully CEL free!
You can find the original schematics and instructions here.
R1 100 K Ohm
R2 1 M Ohm
R3 100 K Ohm
R4 10 K Ohm
C1 4.7 uF Electrolytic
C2 22 uF Electrolytic
D1 1.7v@20mA LED
D2 1.7v@20mA LED
This is meant to fool the ECU into thinking the post-cat O2 sensors are working and the catalyst is within spec.
IMPORTANT NOTE: If you build this, make sure you do not leave PIN 4 on the 555 timer open (floating). This will cause operation to stop and/or reset with even the slightest EMF or input voltage variation. Instead, connect PIN 4 to Input Power. I connected to PIN 8 and it works flawlessly.
The only other improvement would be a smoothing capacitor on the output - just to make the signal more of a SINE wave as opposed to the square wave.
Jon @ Chippernut