o2 sensor simulator

I am working on my wifes car ('03 Corolla 1.8L) and she has a code P0420. I built this circuit R1 100k ohm R2 1M ohm R3 100k ohm R4 10k ohm C1 4.7uF C2 22uF D1 1.7v@20mA LED D2 1.7v@20mA LED I wanted to know how to get the output lower than what I have coming out already. Currently with 12V applied I am getting an output of .000-.832v every 3 seconds. I want to lower that to about an output of .000-.590ish every 3 seconds. I have multisim on my PC but cant figure out how to make the 555 timer work nor change some of the values, I know rookie mistake!

Before I comment on the circuit (like why a LED for D1 instead of a diode?), have you compared the output of the cat's o2 sensor to the front o2 sensor?

Problem solved? Else remove both LEDs and change R3 &/or R4. But do NOT cause any lung or other damage by doing so.

oldspark wrote: Before I comment on the circuit (like why a LED for D1 instead of a diode?), have you compared the output of the cat's o2 sensor to the front o2 sensor?

I built the circuit according to the website that I was following; why they put what component where is beyond me?

oldspark wrote: Problem solved? Else remove both LEDs and change R3 &/or R4. But do NOT cause any lung or other damage by doing so

yes and no. I ended up getting a potentiometer and cutting the output wire in half before it went to the O2 signal wire. I have the value right now down to .640 volts and the light has stayed off for over a week of driving! If the light comes back on, then I will increase the value on the potentiometer until I have it dialed in just right. Thank you

I suspect that circuit has been designed by clueless people that managed to fluke a solution. As long as you realise it is not THE way to fix the problem, and if it is the cat that is faulty (and not the o2 sensor - but that's why I asked my question) then you are pumping out lung damaging acids etc. I'm sure that that solution here would be quite an offence and hefty fines should apply if caught. But having said that, afaik we have no prescribed cat checking, and I use unleaded petrol in my cat-less 1960s vehicles. Thanks for replying. I wasn't sure if you were off checking the sensor or still solving the circuit. PS - see Casper's Electronics Inc. Clean Air Act