OBDII Emissions - Catalyst Monitor Not Ready (3 Viewers)

[Bambusiero]

Sorry, don't have enough experience to answer that.

It may be that there is a large range of acceptable behavior, from new fully functioning cats to old barely working ones.
Three way catalytic converters seem to work by temporarily storing chemicals from the gas stream, and then reacting them with the opposite ones, oxygen (when lean), then combustion products (when rich), back and forth.
A functioning cat (and o2 sensors) shows a low pass filter / smoothing action on the downstream signal.
How smooth? Don't know. May vary a lot.

My recent learnings on this is from a 20 year old 230k mile car with cats that got too degraded (coated with ash) to satisfy the ECU.
I did a hot citric / oxalic acid descale restoration process.
While it did make a noticeable difference visually, and the ECU stopped throwing P0420/P0430 MIL codes, it was not a dramatic difference.
It went from spending no time in the middle, to spending maybe 20% in the middle.
In other words, from square wave to notchy square wave, and that was enough for the ECU.

It would cost me $1500 to get a new OEM exhaust manifold w cats on that car, sooo... not gonna happen.
Not nearly as bad on a Landcruiser. Much simpler, and more reasonable aftermarket options.

99 Lexus GS300 - very high OEM build quality. Mandrel bent stainless steel tube header & metallic core cats. Looks almost new after 20 years.

Hot acid re-circulation setup.

 

[Bambusiero]

Anyway - go ahead and replace O2 Sensor #2.
I'm betting (your money) that you will get passing cat drive cycle for it.
Will be interesting to see your O2 1x2 signal after.

 

[Heckraiser]

Thank you so much for your help! Replaced the rear o2 sensor and got the ready reading in about 30 minutes of driving. Passed emissions and got registration renewed today. I hope this helps someone else in the future.

 

[Bambusiero]

Way cool!
Surprised at how "DC" your O2 1x2 signal is now.
I expected at least a little wigglyness.
Means your cat is really working well, but you did say they are pretty new.

 

[Rwhat]

Good thing it worked out. Anyone have experience using the Autel MK808 for similar diagnostics?

 

[Bambusiero]

Never heard of it. Sounds like something that costs real money? Me too cheap.
Should be the same idea if you can get a time graph of O2 sensor voltage.
Numerical readouts just don't tell you as much, even though it's the same info.

 

[eunique]

Have just been going through this kind of OBD2 DTC readiness business on another Toyota/Lexus vehicle.
Yup - really difficult to drive at certain speeds for given times.

Be aware or this - it can block your DTC progress:
Any existing or pending MIL code will halt the readiness drive cycle.
You must be completely free of error conditions to make DTC progress.

Suggest finding a drive route and time of day that has minimum traffic to get in your way.
Like - 10PM.
However, the stated drive cycle times are more of a driver guideline than a strict exact requirement.
The ECU is following an internal algorithm and adding time up in some cumulative fashion.
Impossible to really know when it's counting or not.

Get an OBD2 reader than shows you DTC status on the fly, like like "Torque" or "Torque-Lite" that you show above - good.

You might find this document helpful (attached):
Lexus Technical Service Information Bulletin - READINESS MONITOR DRIVE PATTERNS, All '96 - '02.

p.s. Suggest going for a drive, watching the O2 Sensor #1 and #2 waveforms (on Torque-Lite).
#1 (upstream) should be banging up and down, 0 - 0.7V or so, in roughly a square wave - normal.
#2 (downstream) should be spending at least some time in the middle, 0.4-0.6 or so.
Doesn't seem to require staying in the middle full time for counting as a functional catalyst.
But - if it's just banging up and down, just like the upstream, then your catalyst isn't a catalyst, it's just a pipe.
> Replace, or do the citric / oxalic acid de-scaling restoration procedure.
> Worked for me on a 20 year old / 230K mile car. Could see the waveform difference before/after.

I know I am reviving this, your posts have helped me tremendously. Mine is 1997 Land Cruiser 80 and I followed what was indicated in this document.

Prior to reading this, I probably drive over 300 miles trying to get my CAT MON INC but was unsuccessful. Mainly it was from what people suggest to drive it around and some youtube videos,none of them proved to be useful.

I monitored The intake air temperature, coolant temp warmed up to appropriate temperature. Then I followed the drivetimes suggested in the document. It did not take long at all. I drove in more remote areas with little traffic so I didn't have to stop much. Also, I used the Torque app with bluetooth adaptor connected. I used a clean page and put it the gauges / monitors I needed. I used intake air temp gauge, coolant temp, MPH speedometer from OBD (so I didn't rely on my speedometer), oxygen sensor graph 1x1 and 1x2. When I was in the proper speed, this is when I would see the bigger difference between the graphs of oxygen sensor 1 and sensor 2.

 

[Bambusiero]

Cool beans, you are now an OBD2 O2 sensor expert!

 

[eunique]

Cool beans, you are now an OBD2 O2 sensor expert!

Haha, not an expert by any means.
I'm just happy I got it to complete and get my smog done.

 

[alia176]

This has been a great read and will help Dx my P0171 code. Thx.

 

[alia176]

Curious about EGR monitor ready parameter - since I have the resistor bypass mod, shouldn't this be ready in my case?