2000 SR5 engine light. 3.4 V6, 5VZFE

[bfrshooter]

Hi, fellas, this is my first post here.
The CEL came on and a dealer wanted $120 to check it. Seems it should be free. This is hard on Social Security. I took it to Auto Zone and the reading came up catalyst system efficiency below threshold, oxygen sensor.
I checked the wiring at the sensors and the colors are not the same as my book. The front one has wh/blue, blue, blk and a wh wire. I get no ground with an ohm meter.
With the key on I get 12.2v at the wh/blue, 2.5v at the blue, 3.02v at the blk and 3.32v at the white. It seems the blk should be ground but I have no idea where a ground point would be.
The front heater shows 1.5 ohms and it is fairly new. It must have been replaced just before I bought the truck, it is a Denso.
I removed both and they were very clean, just needed wiped. The front nuts were not very tight so I suspect a little leakage there.
I put them in tight and cleared the computer.

The rear sensor has wh, red/wh, red and brown wires. The br shows .4 ohms to ground. With the key on I get 12.2v at the wh, 2.5v at the red/wh, .02v at the red and .01v at the brown. The heater shows 13.8 ohms.
Does anyone know what I should do? The truck runs great.

 

[raydouble]

In Google type in - Toyota 5VZFE P0420 - and start reading there are a few things to check. Buckle up for some reading. :bouncy:

 

[Stick Figure]

http://www.ncttora.com/fsm/2003/index.html That may give you a bit more detailed info than your book that you have now. Basically the sensor is probably bad, however i understand wanting to check things out before throwing parts at it.

 

[raydouble]

http://www.ncttora.com/fsm/2003/index.html

They have a new listing for a 96-02 runners (it's for an 02' technically)
http://www.ncttora.com/fsm/1996/SIL/index.html

 

[bfrshooter]

Thanks guys. From what I see the bank 1 sensor 1 is not an oxygen sensor but an A/F sensor and the heater falls in limits. There is also no ground at the plug.
The light has not come back on so I hope it was the loose nuts on the A/F sensor.
I have to remove each nut and get some anti seize on the threads yet.
I might have to invest in a good scanner.
Can anyone suggest one that won't break the bank?

 

[Stick Figure]

My 4runner throws the p0420 code on ocasion as well, but only under certain conditions. The first time it happened was on a trail after going through a bit of water, and since its kicked on after a few hours on the trail at slower speeds, but in normal day to day driving its fine.

as far as a scan tool, you can get a cheap code reader from a lot of places, but if you want an actual scan tool that will give you real time data, then i would look into the auto enginuity products, assuming you have a laptop or PDA. There are some other PC based scan tools as well, but i don't have any experience w/ those.

 

[techno]

Thanks guys. From what I see the bank 1 sensor 1 is not an oxygen sensor but an A/F sensor....

This is one of the differences between California emissions and Non-California emissions spec'd vehicles . If you were not aware that there are two types of exhaust systems out there it might explain why you were seeing wiring color discrepancies.