Check engine light on?

 

If you pick up an OBD2 scan tool from Amazon or your local auto parts store, there should be an option to scan your "readiness codes"

you might need to complete a "drive cycle" as well which is why the smog tech suggested you drive 100mi.

https://www.obdautodoctor.com/scantool-garage/obd-readiness-monitors-explained

I had a similar problem with my Integra, turns out that the problem I had with a thermostat sensor wasn't allowing all of the readiness monitors to fire. Once I addressed that and I drove for a week or so, everything was all good.

 

No check engine light.

I have a code reader, but I'm not sure if it does readiness monitors. The smog tech told me the car was not throwing any codes, but I'll check it out and report back.

Thank you.

 

OK, so my code reader does indicate when sensors are INC, which is helpful. Now at least I know what to look for before I bring it back in to smog. I've been reading on the internet and there's a good dozen or so recipes for completing the drive cycle. I attempted one of them, but since I'm on public roads I don't know how well I could adhere to the prescription. Anyway, I've driven about 500 miles since this all began, freeway and streets, and the cat is still INC.

 

Each "Readiness Indicator" has it's own set of requirements. The Drive Cycle should catch most of them, but not always.

If you fail the Cat Efficiency Test, you'd be logging a P0420 or P0430 code. Good news is that you haven't (yet) failed the test. But for some reason you haven't successfully completed the test the required two times sequentially and passed both times since doing a computer reset as a result of disconnecting your battery. So you need to work on setting up the optimum conditions to achieve a pair of passes.

Without getting into too much detail, the Cat Test runs one time per drive cycle, about 5 to 10 minutes or so after a cold start. Once everything is up to temperature, and if you are driving on a relatively level road (as determined by a load ratio calculation) at a fairly constant speed (40-45 mph works on many cars), the test begins.

In the Catalytic Efficiency test, the ECU actually momentarily leans out the mixture by up to 30% and evaluates the waveform output response of the rear (post cat) sensor in relationship to that of the front AF sensor. It then returns to the stoichiometric point and watches the rear settle out. It then richens the mixture by up to 30% and compares the waveforms again. So it is monitoring the cat’s ability to store up excess oxygen during a lean period and hold on to it, and then release it on demand to cope with an extended rich mixture condition.

The whole deal takes maybe 10 seconds or so, but as I said, it only takes place once per drive cycle, and it takes two runs of this to log a pass and set the readiness indicator. If your whole commute were say stop and go traffic, you might NEVER achieve a green flag.

Hope this helps!

 

Thanks for the information, but you should see how my head is spinning.

My scan tool is pretty basic, but today I noticed that although it says no codes found, if I choose to READ CODES anyway it displays P0420. I guess this means my cat is on the verge of failing?

I will continue to try to achieve the drive cycle. But for P0420, should I replace an O2 sensor before the cat, and which one?

 

And notice that I clearly said "Without getting into too much detail"! That's what happens when you get an engineer involved.... I should have started with "it's complicated!". Sorry about that.

Not knowing how your particular code reader works (I use a laptop with a more complex scan program), it's hard to say. Your cat might be failing the test occasionally, and so it can't achieve the readiness (solid passing) state. It could be a bad mixture (front A/F), bad monitor (rear O2), a contaminated converter, combination of the above. The engine might not be running cleanly (dirty or poorly performing spark plugs, fuel injectors or valve seat deposits), or simply that your driving routine after a cold start doesn't meet the drive cycle parameters for a clean execution of the test.

It could be as simple as running a bottle or two of fuel system cleaner, a sensor or two, or major $$ for cats. If you are totally lost, you might consider paying for professional assistance.

 

There are several reasons for a P0420 code. See this thread for a discussion:

http://www.siennachat.com/forum/62-problems-maintenance-repair/45970-engine-light-code-p0420.html

Search for P0420 and you will see even more threads on the subject.

 

I've been reviewing them. Seeing how I don't actually have the code (a pending code, perhaps?) I would deduce from the previous threads that it is likely my rear O2 sensor is bad, but I'm going to try to get some actual evidence for that by borrowing my local Pep-Boys' OBDII scanner with live data monitoring and hooking it up.

Incidentally, I recently changed out the A/F sensor in bank 1, the PITA one near the firewall, after getting a P1135. That was about 3 months ago. Don't know if that sheds any light.

 

OK, so some progress. I changed out the back O2 sensor (figured it was due, and a cheap way to start before changing the cat.) After driving what I thought was a drive cycle, the Cat monitor is ready! Hooray! But the evap monitor is now INC. There are no pending codes. Does the evap monitor just take more driving?

 

The evap monitor runs approximately 5 hours after you last use the van. It pressurizes the tank and monitors the leakdown rate. The test takes about a half hour to run. I think it's also a two night pass to get a readiness flag.

Approximately 1/2 full tank recommended.

 

I did the drive pattern (or in this case, the driveway pattern) for the evap and that took care of that. All systems go, smog passed. Thank you everyone in this forum for the advice and information.

My layman's conclusion would be that after replacing the B1S1 A/F monitor, the worn out B1S2 O2 monitor could not keep up with the new upstream monitor, creating a pending P0420. So, on high-mileage upstream monitor replacements, also consider replacing the downstream monitor.

 

Great to hear! As you discovered troubleshooting OBD2 readiness codes is no fun!

 

https://www.toyotaparts.metro-toyota.com/READINESS_MONITOR_DRIVE_PATTERNS_T-EG02-003.pdf

Replaced battery in Feb 2018 and was rejected by IL smog check in late March. 2004 Sienna with EVAP Monitor and Catalyst Monitor not ready. Called Toyota dealers and they had no idea....they said just drive it. Tried that for a week and still failed. I used Drive Patterns 4 and 6 from the link noted above and was able to pass. Didn't help that we had almost the coldest April ever, which I think hurt the EVAP reset temperature spread. I got EVAP to clear first, where many posts other places said that was sometimes the last to clear. For Drive Pattern 6, warm it up for 10 minutes or so, 3000 rpm for 10 seconds, and then let it idle for like 20 minutes with AC on.

For the Catalyst Monitor, I used Drive Pattern 4. Finding the right roads and time of day was the biggest challenge. I found a bunch of other ideas surfing and a lot talked about having to coast to a stop with no braking, and I tried several of those with no luck. When I used pattern 4, once I finished the time cycles, I stopped gently but normally, put the car in park, turned it off and then restarted, and did the same drive pattern going back home. Lucky to have some back roads in northern IL to be able to follow the pattern.

In IL if you fail, and then spend like $450 on repairs, they will give you a waiver...what a scam. An IL suggested repair facility said it would be $100 to look at it, but if I let them repair it, they would guarantee it would pass. That was probably going to cost me $450. I wasn't going to let them win and was stubborn enough to not let it go. Do not disconnect the battery that seems to be a popular suggestion. O'Reilly Auto Parts has great OBDII monitors that showed the readiness status and I went there a number of times. AutoZone just has basic engine codes which led me to one of my 3 early failures. I took a picture of the monitor at O'Reilly showing both codes went from incomplete to ok, and showed that to smog check so they would let me retest after failing 3 times.

My family thinks I am nuts but I passed!!! In the future I would never replace the battery within 6 months of from a smog check. Use the link above!