P0420 code

I've got the P0420 catalyst system efficiency below threshold code throwing on my Tacoma. I was just wondering if these readings for the O2 sensors are normal or not?

 

I can’t read graph but I can tell you the most coming 420 issue is exhaust leak

 

the rear sensor graph is suppose to be flat like the front, if the rear sensor graph shows a ton of voltage switching, that equates to your cat no longer capable of doing its job....
One of my specialties was cats & emission related codes related to cats...
No idea if your scanner has an O2 saturation % data available for you to view...
Thats another indicator that will also verify cat is done...

Specs may indicate max% is 84% & youre at 79%, youre done...
If the value is at 40% & max spec is 79%, youre ok....

As stated, a good functioning cat, the rear o2 sensor will mirror the front.
If theres fluctuations, its dead Jim...
Especially while giving it some gas / throttle...

 

Dang Slater awesome

so graphs above are Front02 blue “squiggly” and red rear02 “flat”

means RR front O2 firstly?

or am I WAY off
Thanks

 

That's what Im confused about because the really constant line it shows is sensor 1. So wouldn't that be the sensor before the cat?

 

Upstream B1S1 sensor is an Air/Fuel Ratio Sensor, they don't oscillate like a standard O2 sensor (well they do but the voltage fluctuations are very small).
Downstream sensor is a standard O2 sensor and oscillates from 0-1v, with a good functioning cat it should be pretty steady at around 0.7v

This is a known good from my 2nd gen, it's taken during driving but you can see how steady the downstream is compared to the upstream when the cat is working as it should.

 

Typically
Upstream is front O2
Downstream is rear O2

what Slater’s opinion thou

 

Check for cracks around the pipe to flange on Catalytic converter assembly downstream side. This fixed my po420 code that I was 99% sure was a sensor problem. I used a shop vac and soapy water to find leak and a borrowed HF welder to fix it.

 

Holy Crap Moonrman!

 

$119.99 at HF? Plus $25 for F cable

 

U know, weird thing is
This O2 bung popped out 2 mins from the house. I was late so was so embarrassing driving a POS that sounds like a mustang.

Total trip 1hr 20mins
With the O2 sensor just hanging there
NO CE LITE
???

FI i will take it

 

Cool, you had the cherry bomb muffler in action. Ha ha

 

Probably an exhaust leak. Mine was.