Hi Guys,
Looking for some advice here.
Recently been having some intermittent check engine lights that I have been simply clearing with the code reader. They would stay off for a good while and eventually pop back on. The code was a P0420 cat code.
Anyways, I hadn't been paying too much attention and it became time for an inspection. So I cleared the light on the way to the inspection knowing full well it would not pass. Since the computer was not ready, I have 60 days to get a passing test completed, which will be up at the end of November.
Here's the problem: I have driven the vehicle for over 550 miles and almost six weeks since the computer was reset. Though the CEL is not on, the I/M status is showing as "Not ready" by my Maxiscan 300 reader. All of the sensors are reading either OK or n/a with the exception of the Cat which is showing not ready.
For the record, I had replaced the O2 sensor and cleaned the MAF after I got it home from the insepction. The A/F sensor has only about 30K on it.
I have driven the truck for many short, some medium and a few long trips in that 550 miles.
Can anyone speculate why my cat is not reporting as ready? I would think it will either report in for duty all systems go or trigger a CEL, one way or the other. I am beginning to think I am looking at an expensive cat replacement coming up in two weeks.
Any ideas?

Bumpity bump.
Anyone?

Either the cat actually is bad, or the O2 sensor after the cat is bad. Typically if it's the O2 sensor after the Cat, (bank 1 sensor 2) you'd get a PO136. Sometimes, you'll get a PO420 indicating a bad Cat, but it is just a bad sensor. I'd try replacing the O2 sensor after the cat, before replacing the Cat. Replace that, and then complete a drive cycle to see if that system will set as 'Ready'.

Just an FYI, every time you clear the code, that system will have to see a completed drive cycle, until it will set as 'ready'. Pull the fuse, or disconnect the battery, etc. to reset the computer, and all of the various systems will again have to complete their specified drive cycles, until they will show as 'Ready'.

So doing that on the way to an emissions test, pretty much guarantees that one or more systems won't be 'Ready', when the tech plugs the tester into the OBD II port. Which means a failed test.

Use a Denso sensor only. Amazon usually has the best prices.

I had a p0420 and replaced the o2 sensors and it fixed it. Could be a cat though.

You may want to check your state laws. In North Carolina, if a vehicle is a 2001 and newer, you can have up to 1 system monitor in the "not ready" condition and still take and pass the test. If the vehicle is between 2000 and 1996 you can have up to 2 system monitors in the "not ready" condition and still pass.

Dude you are the fricken MAN . I just confirmed that I can pass in MA with one sensor still not ready. I am going back to the inspection station today to hopefully get the passing sticker. With my luck, I will probably trigger the P0420 on the way to the shop...
Thanks for all the replies guys.
FYI, advice from my uncle (owns a repair shop/inspection station) is that if I have gone this far and the cat is still not ready, it is (they are) likely bad. So I am still not out of the woods.

No problem. Best of luck to you!

I'm in the same situation. I didn't pull the Toyota service history until after I bought my truck. It turns out the PO had replaced the O2 sensors twice and had the OEM cat replacement quoted by the dealer. He never sprung for that one for obvious reasons (~$2,150); however, he was able to get the yearly inspection to pass for the 3 years prior to my ownership. I've skirted past once so far.

Success. Inspection sticker received.
Thanks a lot guys.
Ask and ye shall receive on T4R.org.

Hell, I did not know this.
Good to know especially since I am in NC

In NJ, you cannot pass with a Catalyst 'Not ready.' I checked. A-holes.

Rear Sensor Simulator - Underdog Racing Development

Glad you got it fixed. The above works too!

So glad Florida did away with emissions testing. The old people down here only drive to and from doctors and grocery stores.

The 420 code explains that the sensor that monitors the cats ability to store oxygen is outside of its specs. Which means you are either running too rich or to lean. Stick your finger in the end of your tail pipe. Black rich nothing lean. Lean not enough gas or too much air.Rich too much gas or not enough air.lean is hot and will mean internal temps rise causing oil usage and internal wear. your truck your decision

I thought I'd share my experience on this (long post, sorry). As I got close to my June inspection (every two years) this time, I found I had an I/M Catalyst = Not Ready but no code. I had last cut battery power maybe a month before. I tried my best to adhere exactly to the drive model (see link below) and it just stayed stuck on Not Ready. (Try and drive for 16 min. @ 35-45 mph in New Jersey. You will hit a light, or at least a Stop sign anywhere off the Interstate--and more than one. Try and drive 35-45 on a NJ Interstate for 16 min.! Somebody will shoot you...)

So when I was overdue back in July, I said, "eff this", and put in the URD sim. My sensors were less than 50k on the clock and I had no exhaust leaks. I reset once or twice but no help. I got into a panic as Jan. 1 approached since the stickers change color and shape each year and the last of ones like mine would expire. Still Not Ready and no code and now five months overdue.

Finally, on Dec 22, ready to order new cats without ever seeing a P0420, I checked one last time, and got a 'Ready'. Thank you for the Xmas present 4Runner! Made an appointment and passed inspection the next day. I hope I never have to cut battery power again.

It was probably a trip to Kennedy Airport I made in early December. Thank you Staten Island Expressway and Belt Parkway. Lots of steady driving at <45mph. I guess temps don't get hot enough to complete at the higher speeds we run where I live.

Here is the drive pattern spec, mine is #4 on page 13:

http://forum.ih8mud.com/attachment.p...4&d=1286683966

When it gets warmer, I'm going to pull the sim without resetting. I suspect I didn't need it. Didn't seem to help, anyway.

TheDurk kindly pointed me just now to here, because I have a similar problem, in California, with not being able to smog, because I can't fill the catalytic converter monitor after weeks of driving:

• Why might the catalytic converter monitor be not ready for CA smog test?

I had not seen this drive cycle TSB until now, so, I will read it to see if it helps set the catalytic converter monitor.


Currently in California, you can have up to two monitors (any two) unset, and still pass for a 1996 to 2000 year passenger vehicle; but the smog check station I went to told me otherwise. Right then and there, I called the California BAR at 800-952-5210, who confirmed that information, but the smog check station remained unmoved.



The BAR told me it's their prerogative, but that I could get tested at a California Smog Referee, by calling 800-622-7733, for just the $8.75 price of the certificate, but, I'm late and they don't have appointments for weeks, but I set an appointment anyway.



Meanwhile, I printed out what I thought was the drive cycle (also known as the EPA federal test procedure, or FTP), and repeatedly tried section 5 and 6 below, by setting my phone timer to 3 minutes, and then first driving in 3rd gear, always keeping the tach above 3000 RPM, without decelerating for more than 3 seconds. Then, after doing #5, I subsequently ran #6, keeping the tach between 2100 RPM and 2300 RPM with the air conditioning switch turned on, again for 3 minutes, to complete test #6. But all this was to no avail.


So, I'll download and read the TSB kindly supplied by TheDurk in order to find where my 2wd 1997 5-speed Toyota 4Runner (150K miles, original cat and o2 sensors) tests are that are supposed to set the readiness monitor for the catalytic converter.

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