Can burning too much oil cause a Cat not to set?

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For the longest time my 2002 Toyota Sienna, now with 225k on it, was holding steady at an oil consumption of ~13 .oz per thousand miles. Since this last oil change, about 2,000 miles ago, that has jumped up another 3 oz.

It's smog test time again and I'm having the devil's own time having my catalytic converter monitor set. It's always been a little difficult but never this bad I've driven the two types of Toyota recommended drive cycles three times each and still nothing. Whereas usually doing just the one a couple of times takes care of it.

So I'm wondering if the additional oil im burning could have anything to do with my Cat monitor not setting?

If so, do you think adding a oil thickener, so hopefully less is getting past those piston rings, will help
 
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are you resetting it with a code reader etc? why wouldnt it already be done and ready to go?
 
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So a quart per 1000 miles? If so that’s quite a bit, it could be a problem depending on the phosphorus content of the oil.

That’s more than my old Sienna uses even at over 460,000 miles. How’s the PVC system and the baffles in the valve covers?
 
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In today’s day and age, I’d check under there and make sure no one stole it. 🤣

Once you’re past that part, you should have a code set by now I’d think...catalyst inefficiency maybe? You could infared heat gun before and after the cat. If the temperature isn’t different, the cat’s probably not working. But you probably already know this, and it’s not really what you’re asking. Can burning too much oil not cause a cat to set?

I’d say yes, and I think because this seems like you experienced a gradual issue, with it happening before but clearing up...oil might have failed the cat.
 
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Emissions system readiness requires a specific drive cycle to reset. You can turn off the light but it will still be pending in the computer until it completes the proper cycle.
This is only partly true. The monitor only has to reset after codes are cleared, or possibly after a battery disconnect. After the monitor sets, it stays set until it either fails the criteria for setting a code associated with the system or codes are cleared. The catalyst monitor, nor any other monitor, don't reset every time you restart the car.

As far as oil consumption causing the monitor to not set who knows. Excessive oil consumption can definitely cause a catalyst efficiency code though, but what "excessive" is is going to vary by vehicle and situation. Are/were any codes set?
 
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So a quart per 1000 miles? If so that’s quite a bit, it could be a problem depending on the phosphorus content of the oil.

That’s more than my old Sienna uses even at over 460,000 miles. How’s the PVC system and the baffles in the valve covers?

Castrol makes claims that they’re oils have very low phosphorus levels which can contribute to catalytic converter living longer lives.
 
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This is only partly true. The monitor only has to reset after codes are cleared, or possibly after a battery disconnect. After the monitor sets, it stays set until it either fails the criteria for setting a code associated with the system or codes are cleared. The catalyst monitor, nor any other monitor, don't reset every time you restart the car.
I never said that it did. The OP notes that the monitor has not been reset therefore it must complete the cycle before it will pass an emissions test.
 
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Depending on the scanner used. Some have real time monitoring. You can see the cat working by monitoring front and back O2 sensors. Front sensor will be jagged and back much smoother. I see kschachn has a 1999 Toyota Sienna.
 
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I had a 2006 Chrysler T&C that used oil but not that heavy and it used up (plugged) the Cat in about 120K miles. I'd check and see if a really long drive to warm it up might help, but IMO you are due for a new /cleaned out Cat...

just my $0.02
 
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In GA you need like 3 monitors completed I think, not all of them. I passed with EVAP not ready. You might check your state.
 

djb

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This is only partly true. The monitor only has to reset after codes are cleared, or possibly after a battery disconnect. After the monitor sets, it stays set until it either fails the criteria for setting a code associated with the system or codes are cleared. The catalyst monitor, nor any other monitor, don't reset every time you restart the car.

As far as oil consumption causing the monitor to not set who knows. Excessive oil consumption can definitely cause a catalyst efficiency code though, but what "excessive" is is going to vary by vehicle and situation. Are/were any codes set?

OBD2 introduced the requirement that emissions status be retained across power failures.

This requirement was a combination of experience with the original OBD, where disconnecting the battery was used as a quick cheat, and the new availability of inexpensive high-cycle-life EEPROMs.

That means disconnecting the battery usually doesn't do anything except perhaps clear the radio presets.

Note that on vehicles where disconnecting the battery does something, leaving the battery disconnected for minutes or shorting the battery leads isn't needed. The ECU will reset almost instantly.
 
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My dad has a 2006 Highlander 4-cylinder with low miles and he does the drive cycle before every emissions test. I don't understand why he bothers. I have a 2006 Tacoma 4-cylinder, I've never done a drive cycle and it always passes emissions tests. All in CA.
 
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I never said that it did. The OP notes that the monitor has not been reset therefore it must complete the cycle before it will pass an emissions test.
I get it; the point I was trying to make is that under normal driving conditions the monitor should have set long ago.
 

MichaelRS

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So a quart per 1000 miles? If so that’s quite a bit, it could be a problem depending on the phosphorus content of the oil.

That’s more than my old Sienna uses even at over 460,000 miles. How’s the PVC system and the baffles in the valve covers?
No no. Currently 15-ish Oz every thousand miles. PVC should not be screwed up as I had a new one put in just two years ago but I'll double-check that.
I have no idea about the valve cover baffles or hiw to check them. I'll look that up now
 

MichaelRS

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Castrol makes claims that they’re oils have very low phosphorus levels which can contribute to catalytic converter living longer lives.
Castrol high-mileage has been my go-to oil for the last 10 years. Last couple years had to use Valvoline maxlife a couple of times because of supply chain issues. But other than that I think they're both good oils and I have an average 5,000 OCI
 

MichaelRS

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In GA you need like 3 monitors completed I think, not all of them. I passed with EVAP not ready. You might check your state.
It's the same here in California. the EVAP monitor does not have to be set and my EVAP system has been bad for a while. I do not get that sucking woosh when I undo the gas cap. But it's been that way for the last two, heck maybe even three smog Cycles and I've had no problem with the cat setting until now
 

MichaelRS

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I get it; the point I was trying to make is that under normal driving conditions the monitor should have set long ago.
Yep it neither sets under normal driving conditions nor does it set when I drive the Toyota recommended drive cycles.

I have driven drive cycles number 3 AND 4 three times each and I've also driven some other general recommended drive cycles.
All my other monitors set in jig time. Only the cat monitor and the EVAP monitor remain incomplete.
 
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