2000 4Runner 5VZFE, Catalyst monitor will no set after 2000 miles of driving

David Mobile Technician California Posted   Latest  
Resolved
Emissions
2000 Toyota 4Runner SR5 3.4L (N 5VZ-FE) 4-spd (A340F)
Catalyst Monitor Will Not Set

Hello all. 

2000 Toyota 4runner 4x4 3.4 5VZFE vin JT3HN86R9Y0305215 

This 4Runner will not let the catalyst monitor set. All other monitors are ready. I have completed the exact Toyota drive cycle countless times and also used the vehicle as a daily driver with all driving conditions. The vehicle has been driven around 2000 miles with a couple of resets. There have not been any codes presented, CEL or pending of any kind during this time. 

This has federal emissions standards, I am trying to smog it in CA. The difference is CA gets 2 cats and Federal gets 1 cat AFAIK. 

I went ahead and replaced the cat with a AP Eastern cat. I also replaced both O2 sensors with Denso. 

It had a supercharger on it and it was removed. I do not know of any tuning that has been done to the ECU. I don't think the ECU can be tuned anyhow. The TRD kit relied on the ECU to compensate for the supercharger but it doesn't do a great job as it leans out in in the high rpm range. I removed it to eliminate that variable. 

My LTFT is at -9.1 and STFT at 1.5 not perfect but not too bad. The ECU does know the trans is in drive and as far as all the other parameters, nothing looks out of the ordinary. My ECT is solid and does not dip. TPS is solid as well. Its also got a new MAF. 

The upstream O2 sensor fluctuates as normal.

The down stream O2 sensor never gets above .045 volts. The range is .030 to .045. I think this is too low. The highest I have seen the voltage is .1 on the downstream. This is where is think my problem is. There is fluctuation in the voltage that somewhat mirrors the upstream but it is in such a low range that I can't blame the cat and I figured I'd get a P0137 code for that. Is .030-.045 volts normal?

Any help on this would be greatly appreciated. 

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Stephen Owner/Technician
California
Stephen
 

What is actual ect reading. “Solid” doesn't tell us anything. Cats. won't light off properly if your running too cool.

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David Mobile Technician
California
David
 

The ECT reads between 185 200 degrees and fluctuates due to load normally. ECT temp has no intermittent dips below 176 and the reading is consistent.

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Stuart Mobile Technician
Illinois
Stuart
 

The coolant temp seems a bit low. Most vehicles that I know of normal operating temps are between 220 and 240 degrees

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Tony Owner/Technician
Missouri
Tony
 

That was a fairly normal temp range for this Toyota.

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Mitchell Service Manager
New York
Mitchell
 

You need to look at mode data for converter if available to see if it passes or where it is .. also, you need to know, the enabling conditions for this monitor to run. Years ago, I had a car { don't remember almost same issue } and the AC had to be on, to run the test. SI will always help you

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David Mobile Technician
California
David
 

Hi Mitchell I did look into the 06 data and every test it ran said it passed well with in the parameters. I could not tell what exact test the mode 06 was running since my scanner is and older Snapon unit and did not delineate what each test was. maybe its time for a new scanner. All the conditions met met per Toyotas drive cycle TSB.

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Robert Technician
Michigan
Robert
 

I'd say you need to do one of them Catalysts efficiency test at sometime using both new 02's together and see how far the downstream lags or keeps up with upstream 02 WOT snap. The closer the up & downstream mirror each other on WOT snap throttle the low oxygen storage ..Toyota also 02 switching times but since replaced all good

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Rufino Technician
California
Rufino
 

I been successful ran the cat monitors by driving the car at 55 mph for at least 8 miles, I know we are in California and someone is not possible.

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Jonathan Educator
California
Jonathan
 

David: Good morning Sir, I hope this message finds you doing well. I dealt with a similar issue for one of my students in Redding CA. The Toyota truck he was working on hadn't run it's Catalysts Monitor in over two years, ultimately it was the “Throttle Cable". Someone had overt tightened the cable, taking all of the slack out . During “Deceleration” the PCM wasn't seeing “Closed Throttle” so…

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Interesting
Helpful
Eric Owner/Technician
Wisconsin
Eric
 

David, Your engine temperature is too low, I know the Toyota spec says above 176 degrees F but it needs to be around 195 at a minimum or it won't run the test. While the engine temperature is probably a problem, the lack of rear oxygen sensor activity is definitely a problem. Your rear sensor reading is much too low, either the rear oxygen sensor is faulty, the heater isn't working well…

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Agree
David Mobile Technician
California
David
 

Hi Eric Thanks for your response. Per what you said about the ECT temps, I am going to go ahead an replace the temp sensor and it might change the fluctuating temp. It all looks good on the scanner but maybe just maybe it is the problem. As for the low voltage on the rear sensor, I'm happy that my suspicions have been confirmed. The vehicle does have a small exhaust leak but I figured it…

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Paul Mechanic
Illinois
Paul
 

Don't replace sensor, just reduce frontal area of radiator with a piece of cardboard to see if it lifts average temp and helps stabilize-won't cost you anything and you won't get your hands wet or make a mess. Next, you mentioned the ECU doesn't see it in gear? Not in front of SI, but GM s will not run in park or neutral- the majority are an idle test in gear which I run the cat monitor in the…

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Darren Mechanic
Wisconsin
Darren
 

Small exhaust leak, biasing the 02 sensor.

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David Mobile Technician
California
David Resolution
 

So good news! I went ahead and replaced the temp sensor. I also inspected that “little” exhaust leak and found it to be coming from the flange between new cat, about 4 inches in front of it. The leak was a lot bigger than I thought. The gasket that came with the new cat was very thin. I replaced it with a Felpro gasket and it sealed perfectly. I took it out and the monitor set after about…

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Thanks
Stuart Mobile Technician
Illinois
Stuart
 

Glad you finally have this resolved. Now I'm going to chew you out for not disclosing the minor exhaust leak that would have been the first thing to look at. If you would have addressed that from the get go you would not have came to us and we would not have put our heads together for the cause which is what teamwork is all about and we came out of it learning something, which is the plus that…

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Stephen Owner/Technician
California
Stephen
 

Isnt that what this site is all about? Perhaps he didn't see it, or didn't know an exhaust leak could dilute the 02. Not sure what your gaining by throwing him under the bus.

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Agree
Stuart Mobile Technician
Illinois
Stuart
 

I didn't throw him under the bus. Read my whole response and you might get what I was saying.

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Disagree
David Mobile Technician
California
David
 

Yes, I should have looked into the exhaust leak. It was not noticeable at idle until I got under the car and felt around. But that what places like this are for. When you chasing your tail into a dead end and don't notice a blind spot in your diag until some one says “oh hey, did you check for xyz” and the light bulb goes off. Lesson learned, don't disregard exhaust leaks lol! Thanks for you…

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Tony Owner/Technician
Missouri
Tony
   

You can smoke the exhaust from the tail pipe forward (stuff any additional tailpipes as necessary), or for aggressive leak finding I find a shop vac set to blow air into the tailpipe makes audible or soapy water testing easy. Any leak anywhere near the exhaust sensors should be fixed before chasing oddball sensor trends or cat monitor not run issues. I don't see where you compared the new ECT…

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Eric Owner/Technician
Michigan
Eric
 

Can we assume you meant .30- .45 volts on the downstream? Even this would alarm me, a healthy cat usually is in the neighborhood of .60- .70 volts. What was the value of the downstream after repairing the exhaust leak? Coolant temps may affect the monitor but can't see why it would affect the actual function of the cat. Anytime the 02s are really low, smoke the exhaust system or at the very…

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Robert Technician
Michigan
Robert
   

Probably just had another used motor stuck in it and those really suck on the rack no where to lift it, i can see an exhaust getting by

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