Engine light stays on after changing 02 sensor on my 2000 toyota tundra code read o2 sensor

If you are getting 0 Volts on O2 sensor #1, the front sensor is probably bad or has a wiring problem (usually the sensor at the catalytic converter inlet is "O2 1"). Check the wiring first, especially at the sensor connector. It could even be corrosion in the connector terminal.

Did you change right sensor?

There are actually 4 o2 sensors on tundras. one in front and one in back of each cat.

Make sure it is a o2 malfunction before changing it,the o2 just gives information mainly,the generic code is a mass air flow sensor,and this would be more like what the problem is.

Your van has four o2 sensor's, the code should tell you which one is bad for exsample code should be like,
o2 sensor bank 1 sensor 1 or 2
o2 sensor bank 2 sensor 1 or 2

Also make sure you don't have a vacum leak.

Code P0420 is a code for Catalyst efficiency. The computer is seeing the post Catalytic converter o2 sensor having too much activity. The Cat. should be cleaning the exaust of Hc, co, and Nox. The post cat o2 will read the o2 content in the exhaust and if it moves up and down too much or to high and low, the computer interperates that as the cat not ridding the exhaust of it's pollutants. This indicates that the converter is unable to preform properly. The problem could be a bad cat, o2 sensor (Pre- and/or post cat)or o2 sensor wires, or an air fuel mixture problem that has caused the cat to fail. Many other engine operating system failures can cause the converter to not work properly.

Could be a problem with the Catalytic Converter or oxygen sensor (H02S bank 2 )

vehicle may have more than 1 o2 sensor. have u checked to see if it has more? most vehicles have more than 1

Some time when you got new sensor s they have to be coded so the cry recognise them and some after market items aren't as good so try and get an oe part.

I had to replace both o2 sensors on my 2002 Tundra after about 50K. Toyota recalled this problem afterwards and refunded my money. My solution to you is to not worry about which one is bad and go ahead and replace both, because I had one bad and before I could replace it the other went bad also. PS: You'll have to purchase a special socket to remove them and unless you pruchase the Toyota product ( I used O'Reilly parts), you have to cut and splice the wires with a waterproof splicing kit included with the sensors. Just follow the instructions, not a hard job.