09 Sion TC

ghost

ghost

Well-Known Member
Joined
May 25, 2006
Location
Hartsville/Camden,SC
So my wife has had this car sine new. It has thrown a PO420 code a couple times. It is using some oil. 180K or so miles. I know some of you guys love your Toyota's and its you that I'm asking this. Are the two related? It was suggested that the oil burning is causing the o2 to read wrong and then that is causing the code. My first thought is that if it's using oil would that not be valve seals? Thoughts?
 
Whens the last time you replaced the O2 sensors? Are they original? That's the easy thing to try if you haven't already, as they have a finite life and aren't expected to last 180k miles.

Oil residue can potentially poison both the O2 sensors grid and the cat converter matrix, either of which can cause the P0420 code.
 
That engine in those years is known for oil consumption due to low ring tension. If you came into my shop I would recommend replacing the O2 sensor (with a good one ie: NGK, NTK) but would caution you that Toyota's are pretty good at throwing the correct codes for the problem and that a converter my be in the near future.
 
Well if it comes back I'll look at replacing the O2. Thanks.
 
You could try the cataclean stuff. I've heard mixed results. Likely if it's only p0420 (below efficiency), it's very likely just the converter. You can view scanner live data to confirm that. Downstream voltage should slowly change, & upstream cycles rapudly. There are codes for sensors being slow to respond, as well as being below output voltage. Yes, it is also very likely that it was/is caused by the oil consumption. New converters differ in prices also due to differences in the actual converter quality. New oem will out last aftermarket, always. (Batter/more/higher quality catalyst) although an aftermarket will work just fine, especially considering it's probable that it will end up recurring after some period of time. II have also seen vehicles report p0420 for running on regular vs premium fuel. (Lincoln aviator that calls for high octane) That's my dollar three eighty contribution.
 
So it showed up again. I plan on getting an O2 today and swapping it in. I assume I need the one after the cat. I also am assuming that is a downstream one listed at parts stores. Please correct me if I'm wrong. Are they different sensors? I would think if they are measuring the same thin that they are the same.
 
ghost said:
So it showed up again. I plan on getting an O2 today and swapping it in. I assume I need the one after the cat. I also am assuming that is a downstream one listed at parts stores. Please correct me if I'm wrong. Are they different sensors? I would think if they are measuring the same thin that they are the same.
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The downstream is after the cat, and it is usually a narrowband O2 sensor because it's primary job is to determine the effectiveness of the cat (it is compared to the reading from the upstream O2).. The more expensive and accurate wideband O2 is before the cat, and is the one that the ECU uses for fueling strategy. So yes, they are different for late-model vehicles.
Get the good brands, like Denso or whatever is the OEM brand for Toyota.

Don't get a cheap one, and don't get anything universal. It will usually not work, and you'll be in the same non-functional boat as before, but now you'll have to buy a second part that cost more and works better. You cannot return a used O2 sensor.
 
Stuntman Autoworks said:
Do you live in a county that requires obd inspection?
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No but this car is being sold to my step son and he is not mechanically inclined. I just want to make sure he knows what must be done to keep this car running good like it is now. Trying to teach him some things.
 
ghost said:
No but this car is being sold to my step son and he is not mechanically inclined. I just want to make sure he knows what must be done to keep this car running good like it is now. Trying to teach him some things.
Click to expand...

If it’s burning oil it will die in untrained hands, it won’t be something they think about because well, I never had to before.

The sense of importance / urgency won’t be there until he looses an engine or something else bad happens. Went thru this with my brother in law, “ I didn’t think it was a big deal”
 
Which motor is in it? I do know some had oil consumption issues, which would lead to the converter fouling. I have heard of cleansing the converter (removed) with some solution but don't recall what or if it was effective. If you have a scanner with live data view, before you replace any sensor, post up a pic of the upstream and downstream sensor output graphed, at idle and part throttle. If the downstream sensor output mimics the upstream sensor output, the converter is definitely not burning unburnt HC. I've heard of using a spark plug non fouler on the downstream sensor to pull it out of the exhaust gas flow to get rid of the code (as well as an electrical circuit solution, without the non fouler, but haven't tried on any later models, as ive heard it doesn't work due to advanced detection ability) I've heard mixed results of using the non fouler as well, thoigh there are companies that sell stand alone oxygen sensor simulators.. or you could tune the code out if you can find someone with a tuner for it - I'm fairly sure they might exist, being a Scion/Toyota. Simply replacing the converter - whether it's a direct fit (check Amazon) or where you can weld in a universal, will work for a while - at least until it gets contaminated again - which depending on rate of oil consumption may be years, months or days. Leaking injectors will cause converter failure as well. Determining the cause of the cat failure is crucial to preventing a repeat failure. (There's another option - I have contemplated developing a CEL reset box that when wired in and turned on simply erases The codes every key on, as p0420 is usually a 2 run cycle to fail.. intention of device willw be for individuals desiring to eliminate the light without repair in non emission places and not for installation except by customer request)

Sorry for the book.
TL;DR - don't throw parts at a problem, replacing cat without diagnosing failure will be a repeat failure (though not necessarily immediately)
 
Last edited:
Blkvoodoo said:
If it’s burning oil it will die in untrained hands, it won’t be something they think about because well, I never had to before.

The sense of importance / urgency won’t be there until he looses an engine or something else bad happens. Went thru this with my brother in law, “ I didn’t think it was a big deal”
Click to expand...

I think he will be ok. He is buying the car and is actually able to fix and make things but is lazy IMHO. He's had a couple weeks with no car and I think that will help.

a_kelley said:
Which motor is in it? I do know some had oil consumption issues, which would lead to the converter fouling. I have heard of cleansing the converter (removed) with some solution but don't recall what or if it was effective. If you have a scanner with live data view, before you replace any sensor, post up a pic of the upstream and downstream sensor output graphed, at idle and part throttle. If the downstream sensor output mimics the upstream sensor output, the converter is definitely not burning unburnt HC. I've heard of using a spark plug non fouler on the downstream sensor to pull it out of the exhaust gas flow to get rid of the code (as well as an electrical circuit solution, without the non fouler, but haven't tried on any later models, as ive heard it doesn't work due to advanced detection ability) I've heard mixed results of using the non fouler as well, thoigh there are companies that sell stand alone oxygen sensor simulators.. or you could tune the code out if you can find someone with a tuner for it - I'm fairly sure they might exist, being a Scion/Toyota. Simply replacing the converter - whether it's a direct fit (check Amazon) or where you can weld in a universal, will work for a while - at least until it gets contaminated again - which depending on rate of oil consumption may be years, months or days. Leaking injectors will cause converter failure as well. Determining the cause of the cat failure is crucial to preventing a repeat failure. (There's another option - I have contemplated developing a CEL reset box that when wired in and turned on simply erases The codes every key on, as p0420 is usually a 2 run cycle to fail.. intention of device willw be for individuals desiring to eliminate the light without repair in non emission places and not for installation except by customer request)

Sorry for the book.
TL;DR - don't throw parts at a problem, replacing cat without diagnosing failure will be a repeat failure (though not necessarily immediately)
Click to expand...

Unfortunately all I have is a $20 code reader right now. I guess I need to research and see what one cost with live data... I was talking to snappy about getting an older snap on but have not gotten anywhere with that. Thanks all for the help.
 
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