If you know it's only the heater, you can also keep on driving till you have the money to get it replaced. that heater is only to warmup the sensor faster.. don't worry about the cel, just read it out every couple of days, so you know things are not adding up.
denso oxygen sensor on ebay is ~80-100$, only things needed for replacement is a good 22mm spanner.

check for obd scanners on amazon, propably its only 3$ more, but you have it in 2 days and not 25.

 

The issue with driving the car with the 02 sensor tripping the CEL is the ECM will go to open loop and the car will run considerably rich. Will get poor fuel economy and also put necessary carbon deposits in the catalytic converter.

 

so decided to replace O2 sensor heater and had mechanic clear codes... did a few LONG drive cycles over the course of 5 days. Today on way to autozobne to confirm monitors ready my freakin check light came on = devastated.

So now i have code P0430

obviously cannot afford new converter but wanted to know from the great experts on this forum:

i have 2000 lexus - so if i complete O2 sensor / O2 sensor heater / evap. system =3 total
i could pass emissions with catalytic converter - not complete???

Plan to reset check engine light today and hopefully end the nightmare...

thanks

polo

 

This is what I used...

I drilled out one of the two spacers using a 1/2" bit. Then fitting the O2 sensor on the drilled spacer.
P0420 fixed for about $6.00.

Double check for exhaust leak then try it...