[MarsSVTF]

2002 SVT Focus, 95K miles.

Using some software if found on line and my ELM327 bluetooth OBD2 scanner i ran some tests on my o2 sensors and im trying to find out if these point to my cat or #2 sensor is dead.

 

[MarsSVTF]

I just read this:

The front O2 switches back, and forth between rich, and lean. rich/lean/rich/lean/etc... If the cat is doing it's job, it will be "cleaning" the exhaust, and the rear O2 will barely switch. If they both switch insync with each other, it's because the cat isn't "cleaning" the exhaust.

So now im more concerned since this code popped up only after i did the timing belt.

 

[Marde]

Your pic and what it displays has "issues".

BTW:
O2S11 (your pic) = O2B1S1 (what I call it because that is what Torque calls it)
O2S12 (your pic) = O2B1S2 (what I call it because that is what Torque calls it)

The O2B1S2 (rear O2 sensor) has a low voltage of 0V and a high of 0V; this despite the couple of voltage peaks shown in the pic-> the scale or peaks have some kind of error in the datalog/screen grab or in the software. The O2B1S2 should "most often" be hovering in the half-volt range (.5V).

The datalog (or the screen grab) is less than 2 seconds; not enuf time.

O2 sensor performance data should be recorded when cat is hot and engine is at about 2500 rpm.

You might have a problem with the O2B1S2 sensor or wiring. Please do some more datalogs or use another (not a O-scope style) type of gauge to monitor O2B1S2. An Android App "Torque" (is free) might serve you better.

You can do some good (cat health) troubleshooting yourself at home with an IR Temp gun & a Scan tool to monitor O2 sensor performance. Please watch this video->
https://www.youtube.com/watch?v=9VZ5K8n5jj0

For the Scan tool tests shown in the video, you can use the Torque app instead. Good scan tools with (fast data sample rate) O-scope functionality are always better than the slow ELM327/Torque crap that you and I use.

 

[Marde]

BTW my O2B1S2 struggles to stay in the half-volt range; has lots and lots of voltage dips; so it acts like the cat is failing. Thankfully, my PCM has not set a P0420 yet.

My Cat temps (inlet verses outlet temps) are also failing. Strange my PCM has not set a P0420 yet.

 

[Lukemc]

Im currently hanging out with a P0420 code so IM going to keep an eye on this thread. Post what you figure out!