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

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

Why would a catalytic converter monitor consistently (for weeks of daily driving) not be ready for a smog test?

Two weeks ago I went to a California smog test station, and they said my 5-speed '97 2wd 4Runner with 150k miles (with original cats and oxygen sensors) would fail because the catalytic converter monitor wasn't ready.

They said drive 15 minutes on the highway, and it would become ready, but, it has been over two weeks and it's still not ready - and I've driven between 50 and 60 steadily on the highway for hundreds of miles.

All other registers are full, and there are no pending or set codes.

I'm stumped, and need your experienced advice:
What could possibly make a catalytic converter register never get ready?

When I googled, I found that some people tried replacing oxygen sensors, but, mine seem to be fine (so I wouldn't replace them unless/until they indicated they're actually bad).
If the detail helps for you to advise me, there are apparently two different oxygen sensor monitors (02S and H02S), but both are fully set and there are no diagnostic trouble codes whatsoever.

So, with the oxygen sensors ready, and all other monitors full, why, after weeks of driving on all types of typical conditions, would the catalytic converter monitors not show they are ready?

What do I need to do to force the catalytic converter monitor to be ready?

There is a TSB that describes the drive cycles required which I have attached below.

This thread has some good info including my own painful experience.

http://www.toyota-4runner.org/3rd-gen-t4rs/154614-cat-not-ready-inspection-question-p0420.html#post1572874

Yeah, the driving pattern is pretty complicated, not just 15 minutes on the highway. It also requires several consecutive bad readings from the CAT/O2 to actually finish and trigger the CEL. If your CAT's are borderline, then it can take a really long time for the test to finish with either a fail or pass. Mine would go months at a time at "not ready" before finally triggering the CEL.

To force it to ready, you will have to get an O2 simulator, but those aren't legal for road use. Otherwise you can try cleaning your CAT's (look it up on youtube) or just replace them and wait for the test to finish again.

TheDurk said:

There is a TSB that describes the drive cycles required which I have attached below

Click to expand...

Thanks for that TSB!

I appreciate the help. I'll look at the TSB to see what to do to get the catalytic converter test to complete on my 1997 5-speed 4-cylinder 2wd 4Runner.

Before I had seen your TSB, I had gone almost crazy trying to get the catalytic converter codes to set, because I was following test #5 and #6 of THIS test procedure:

1. I left the smog check station, because they refused to run the test.
2. I got on the highway, and set my cellphone timer to 3 minutes.
3. I tried to put the transmission in 4th, but I couldn't get the tach and speed to agree with the chart above, so I opted to just follow the RPM and time requirements.
4. I put the stick in 3rd gear, and kept the tach at > 3000 RPM, without decelerating for 3 seconds, for the entire 3 minutes (heading south on the 101 towards Gilroy, to avoid traffic).
5. Then I reset the 3-minute timer, and put the transmission in 4th gear, and then kept the tach at 2100 to 2300 RPM, with the air conditioning switch turned on.
6. On the way back up from Gilroy to San Jose, I repeated this procedure with as many variants as I could think of.
7. Back at the smog check station, the catalytic converter monitor was STILL "NOT RDY".

In sheer frustration, on my way home, I had called the California Bureau of Consumer Affairs to talk to a BAR Technical Advisor, at 800-952-5210. I spoke to Glen who told me the following:

• Vehicles from 1996 to 2000 can pass California smog with up to two (any two) registers unset. Soon, he said, that will drop to one register (any one other than the fuel evap) in the future, based on new rules recently put in place.
• Currently, vehicles from 2001 onward can pass with one register unset, which will go to zero in the future.
• It's up to the smog station whether they want to test you or not, and, since mine wouldn't test with any registers set, Glen told me I am eligible to go to a "Smog Check Referee".
• I called the 800-622-7733 Smog Check Referee number, and set up an appointment, at the Evergreen Community College, for two weeks from now. The cost is just the $8.25 for the certificate.
• In the future, OBD test readings will be used instead of the dynamometer, but, the infrastructure isn't in place yet.

Nelsonmd said:

Yeah, the driving pattern is pretty complicated

Click to expand...

Thanks for that information, as I had thought the EPA drive cycle was simpler than it turns out to be.

For example, the technical advisor, Glen, at the California BAR (800-952-5210) told me that it's impossible to set the catalytic converter monitor the way I was trying to do it, simply because, he said, it has to be from a "bone cold" start. He said that you have to "gently" get onto a highway as soon as you can, from a bone-cold start, and then run the highway section of the test. If you are far from the highway, he said, you'll warm up the cats too much to run the test. In other words, he said, you'll NEVER be able to set your monitors, depending on your commute from home to the highway.

He also said if a temperature sensor doesn't indicate the engine went from cold to warm during the test, the readiness monitors won't be set.

Glen said the cat and the fuel evap monitors are some of the hardest to set (e.g., the fuel evap requires the tank to be between 1/4 and 3/4 or it will never run the test!).

I converted the PDF TSB TheDurk kindly provided to JPG, and I will post the relevant page for my 1997 5-speed 4-cylinder 2wd 4Runner once I figure out which test I need to run to set the catalytic converter monitor.

EDIT:
Page 4 of the document shows the following chart for our vehicles, with my 4Runner type circled in blue, showing the relevant test to be "Catalyst (O2S Type)".
So, I'll look deeper into the TSB to find what specific test sequence to run, in order to test that.

I think the relevant page for my 4Runner is page 12 of the beautiful document TheDurk kindly provided.
I also noticed that the temperature at the start is DIFFERENT than what the California BAR technician stated, so, once again, I'm confused.
But, I tend to think that Toyota knows the 4Runner better than the California BAR, so, I'll try to decipher exactly what I need to do from the following transcription.

Preconditions:
The monitor will not run unless:
- MIL is OFF.
- ECT (Coolant Temp) is 176°F (80°C) or greater.
- IAT (Intake Air) is 14°F (–10°C) or greater.*
*For 2002 MY and later vehicles:
The readiness test can be completed in cold ambient conditions (less than 14°F / –10°C), if the drive pattern is repeated a second time after cycling the ignition OFF.

Drive Pattern Procedure
- Connect the OBDII Scantool to DLC3 to check monitor status and preconditions.
- Note the IAT (Intake Air) value during engine startup.
The driving time must be adjusted during step “a” based upon IAT (Intake Air) value at startup.

a. Drive the vehicle at 40 – 55 mph (64 – 88 km/h) for the time described below:
If IAT (Intake Air) was less than 50°F (10°C) when the engine was started,drive for 7 minutes.
If IAT (Intake Air) was greater than 50°F (10°C) when the engine was started,drive for 3 minutes.

b.Drive the vehicle at 35 – 45 mph (56 – 72 km/h) for approximately 7 minutes.

NOTE:
Drive with smooth throttle operation.
Avoid sudden acceleration.
Avoid sudden deceleration as much as possible with the throttle fully closed.

If readiness status does not switch to “complete,” ensure preconditions are met, turn theignition OFF, then repeat steps “a” and “b".

NOTE: The readiness status may not switch to “complete” after the first drive pattern trip if aPending Code has been set (first trip for a two–trip DTC).
- Pending Codes are available from the DTC Info Menu in Enhanced OBDII.
- Pending Codes indicate a POTENTIAL problem was detected. A second trip isneeded to confirm the DTC prior to diagnosis.
- Once a second trip is completed, a current DTC will be stored.

mom said:

Why would a catalytic converter monitor consistently (for weeks of daily driving) not be ready for a smog test?

Two weeks ago I went to a California smog test station, and they said my 5-speed 997 2wd 4Runner with 150k miles (with original cats and oxygen sensors) would fail because the catalytic converter monitor wasn't ready.

Click to expand...

I thought you were going to replace your O2 sensors at some time in the past. I could have sworn I told where to buy them (Amazon).

At any rate, after 17 years the Bank 1 Sensor 1, and Bank 1 Sensor 2 O2 sensors are likely ready for replacement.

The before Cat sensor will affect your MPG, the after cat sensor monitors the Cat, and can give the "Cat Not Ready" code. The Cat can be fine, and you'll still get the "Not Ready", just due to a worn out sensor.

The Cat could be bad, but I'd try replacing the sensor first. That often solves the problem, and is a lot cheaper than a new Cat.

Just a word of advice, pulling the EFI fuse, or disconnecting the battery temporarily, will reset the ECU. You will then have to complete a drive cycle that satisfies each of the various systems, before those systems will show as "Ready".

So don't pull the EFI fuse, or disconnect the battery, and then drive directly to have an emissions test. You will likely fail due to various systems showing "Not Ready".

02SE said:

At any rate, after 17 years the Bank 1 Sensor 1, and Bank 1 Sensor 2 O2 sensors are likely ready for replacement.

Click to expand...

On the one hand, it makes sense that parts don't last forever, but, on the other hand, if the oxygen sensors were bad, wouldn't they be throwing a code right now instead of the catalytic converter not completing its tests?

mom said:

On the one hand, it makes sense that parts don't last forever, but, on the other hand, if the oxygen sensors were bad, wouldn't they be throwing a code right now instead of the catalytic converter not completing its tests?

Click to expand...

The parameters for the sensor fail codes are very gross, as it were...heater burnt out, sensor circuit open or short, voltage out of range. Sensor performance can degrade in things like response time without throwing a fail code. So...not necessarily.

TheDurk said:

Sensor performance can degrade ... without throwing a fail code.

Click to expand...

This makes sense.

Unfortunately, I have little experience with this type of problem. I looked them up once, but, can't find that reference anymore. Luckily, I think we had concluded that replacing the oxygen sensors doesn't seem to be all that difficult.

I guess the downside of replacing the sensors is just the cost & effort (do you buy these OEM or can aftermarket suffice?).

I'm not sure what the upside is, other than maybe that will "fill" the catalytic converter register (which only matters for smog inspection); but, with the smog-check referee appointment now scheduled, I don't even need to do that.

I guess if the oxygen sensors are adversely affecting fuel mileage, the concrete upside might be better mpg efficiency (I never check it though).

Is there any other upside to replacing the oxygen sensors

You only want the OEM Denso sensors. You don't have to buy them from Toyota. Amazon or Rockauto.com usually has the best prices. Get the Denso part number here:

Find My Part | DENSO Auto Parts

At your mileage on original sensors I would just change them. They don't owe you anything; they are past end-of-life. If the front sensor is the problem, changing it probably will improve mpg as well.

TheDurk said:

changing [the front sensor] probably will improve mpg

Click to expand...

Thanks. I wasn't sure what positive effect they'd have, so, I appreciate the insight.

TheDurk said:

You only want the OEM Denso sensors.

Click to expand...

Thanks for that advice as I don't have the experience to make the brand decision on my own.

TheDurk said:

Get the Denso part number here

Click to expand...

Thanks for that search tip, and the OEM brand name.
Going to that URL, it seems the two part numbers I would want are:

• 234-4153 (about $60)
• 234-4162 (about $60)

I'm googling right now to see how best to TEST the sensors, since I rarely replace parts without first attempting to diagnose that they're actually bad - unless - it's the only option left.

Thanks for all your help and advice!

By way of update, I took my 4Runner to the special state-run Consumer Assistance and Referee Center (aka, "smog test referee") today:
Two "referees" spent at least 45 minutes going over the car, inch by inch.

• They first marked all the scratches and made me sign the waiver.
• Then they put the OBD scanner on it, and agreed with me that the catalytic converter monitors were still not ready.
• Then they started the engine, with the hood open, and, with a flashlight, the two of them went through a checklist for at least 20 minutes, visually checking the EGR, oxygen sensors, hoses, oil leaks, and even wisps of smoke were noted, all with the engine running.
  • (They told me the smoke test here doesn't fail the car, but the ending smoke test will fail it.)
• Then they "kicked" the gas pedal, and wrote down how much smoke was emitted from the tailpipe the SECOND time they did that.
  • (It can fail if it is more than 8 feet of smoke!)
• Then they drove it onto the dynamometer, and revved the engine up for the low speed and high speed tests.
• Then, they opened the hood AGAIN, and looked for smoke
  • (This final visual smoke test, they said, could fail the vehicle.)
• They pressure-tested the gas cap off the car, and they crawled down below and looked underneath for something, I don't know what.
• At one point, they pulled out a fat brown Mitchell book off the shelf, and earnestly discussed something, I don't know what.
• Finally, after almost an hour of testing the vehicle, they sat down at their desk, and asked me to pay only for the $8.25 smog test certificate!
  • (The actual test was free.)

It passed smog (without the catalytic converter readiness monitors ever having been set)!

Catalyst monitor not ready finally FIX.

Had the same problem with Tacoma. Ask my mechanic friend and suggested changing Thermostat. Bingo! Set last two remaining monitors: Catalyst and Evap> Apparently, thermostat is staying open and thus coolant not reaching 176 degrees which is the precondition set by programmers for the monitors to even start.
:roadkill:
In addition, Hyundai released a service bulletin in the internet explaining such condition why catalyst monitor wont get ready.
If only those dumb smog checkers would tell you how to fix it and not keep telling you to keep on driving, then a lot of time and money and stress would be avoided.
Hope this helps. Booyah!!!

bong said:

Catalyst monitor not ready finally FIX.

Had the same problem with Tacoma. Ask my mechanic friend and suggested changing Thermostat. Bingo! Set last two remaining monitors: Catalyst and Evap> Apparently, thermostat is staying open and thus coolant not reaching 176 degrees which is the precondition set by programmers for the monitors to even start.
:roadkill:
In addition, Hyundai released a service bulletin in the internet explaining such condition why catalyst monitor wont get ready.
If only those dumb smog checkers would tell you how to fix it and not keep telling you to keep on driving, then a lot of time and money and stress would be avoided.
Hope this helps. Booyah!!!

Click to expand...

That's weird. I had my coolant replaced and T-stat replaced a couple of months ago at the dealership. Drove for over 1500 miles and it still won't read at the smog check.

I am starting to think that this is just some conspiracy to get consumers to spend more money...to getting a new car so DMV can charge you more for licensing fee (car tax).

I have the same problem. I replaced a ton of parts indicated by the error codes and the catalyst module, which never got an error code, won't reset. I have an appointment with a smog referee this week.

310Nesta said:

I have the same problem. I replaced a ton of parts indicated by the error codes and the catalyst module, which never got an error code, won't reset. I have an appointment with a smog referee this week.

Click to expand...

Don't know if you have the '01 or '02 V6 3.4 litre, but I had this mechanic diagnose it and it turned out out to be an intermittent throttle position sensor. Unfortunately, those model years has the TPS and throttle body as a one piece unit, so to replace the TPS, you'll need to replace the whole throttle body with it.

My mechanic manually adjusted the TPS to be within a certain range. In addition, I replaced the back O2 sensor, front A/F ratio sensor, all spark plugs, spark plug wires, PCV valve and grommet, and checked for vacuum leaks in the hose for PCV valve. Drove for 300 miles and then all monitors were ready.

Incomplete Catalyst issue

Hello Everyone,

So I have the "Incomplete Catalyst" issue and cannot seem to get drive cycle to clear it. I have replaced the following:

- o2 both front and rear with Denso's
- Cats from a donor
- New spark plugs
- New wires

No CEL light or any other codes. I have driven over 1000 miles and still does not clear. All other drive cycle tests clear quickly.

I am pretty desperate since I just purchased and need to register. I bought from an auction so I need to smog asap.

Any suggestions would be appreciated. I have tried the drive cycle as per the TSB with no luck.

Will using the URD o2 simulator complete the Catalyst cycle?

Thanks,

redlo said:

Hello Everyone,

So I have the "Incomplete Catalyst" issue and cannot seem to get drive cycle to clear it. I have replaced the following:

- o2 both front and rear with Denso's
- Cats from a donor
- New spark plugs
- New wires

No CEL light or any other codes. I have driven over 1000 miles and still does not clear. All other drive cycle tests clear quickly.

I am pretty desperate since I just purchased and need to register. I bought from an auction so I need to smog asap.

Any suggestions would be appreciated. I have tried the drive cycle as per the TSB with no luck.

Will using the URD o2 simulator complete the Catalyst cycle?

Thanks,

Click to expand...

Mine finally cleared. What happened on mine was the throttle position sensor. It was intermittent so wasn't bad long enough to trigger a code, but enough to not allow it to be ready. Had a mechanic manually adjust it. I had a little hesitation accelerating from a stop at the time.

TPS on '01 and '02 model years are fused together with the throttle body. So in essence, to replace the TPS, you have to replace the throttle body along with it. Poor design on Toyota.

jh818 said:

Mine finally cleared. What happened on mine was the throttle position sensor. It was intermittent so wasn't bad long enough to trigger a code, but enough to not allow it to be ready. Had a mechanic manually adjust it. I had a little hesitation accelerating from a stop at the time.

TPS on '01 and '02 model years are fused together with the throttle body. So in essence, to replace the TPS, you have to replace the throttle body along with it. Poor design on Toyota.

Click to expand...

I have a spare throttle body from a donor vehicle. I will try replacing it this weekend. At this point I am desperate. lol