Do I need to buy 2 upstream and 2 downstream sensors?
new O2 sensor purchase question (1 Viewer)
- Thread starter Clunky
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If you want to replace them all? Yes.
Trunk Monkey
Moderator
Reason you're thinking you need to replace all four all at once?
- Thread starter
- #4
The rig is 20 years old w 200K miles and they’ve never been replaced. I figured I’d just replace them all.
I have been in the process of replacing a lot my electrical components that other people seem to have problems with. My 2001 is approaching 20 years old and I plan on keeping it for a very long time. I can either scramble to replace the stuff when it goes out or do it at my convenience.
Stuff replaced in the past 3 years:
1.) High output alternator - DC Power, Inc. (appx.$650.00)
2.) EFI relay - Toyota (appx. $60.00)
3.) MAF Sensor - Toyota (appx. $180.00)
4.) Both upstream 02 sensors - Denso (appx. $140.00)
5.) Batteries - Bosch (appx. $180.00)
6.) Iridium Spark Plugs - Denso (appx. $100.00)
7.) All 8 Spark Plug coil packs - Denso (appx. $500.00)
8.) New Fuel Pump - Denso (appx. $150.00)
So for approximately $2,000.00 of parts, I trust my 2001 LX to be as dependable as 99% of the cars on the road.
I also spent appx. another $2,000.00 of parts on new AHC globes, changing all fluids, belts, hoses and etc. So it also drives and rides as good as 99% of the SUVs on the road too!
Next project that I am just waiting for an opportunity is replacing my ignition key rod.
P.S. I keep all the old parts that are still functioning ok as spares and to troubleshoot future problems with.
Trunk Monkey
Moderator
If you don't have a CEL related to them, no reason to replace, better uses for the funds on other actual PM items.
Some owners with a verified bad sensor would be trying to figure out how to "fix" the sensor for free and then on the other side we have @Clunky replacing all 4 preemptively, haha!
I'd just buy the upstream ones preemptively. The upstream control your engine. Downstream sensors monitor the cats for emissions control efficiency, but I don't believe they'll have any impact of anything aside from throw a code when they start to fail.
I always thought that was the case as well, but then I read this: Dealing With Sensitive Types: Toyota A/F Sensors | MOTOR
"Since Toyota allows the rear O2 sensor a surprisingly large authority over fuel trim, you’ll want to test it carefully as well. (Many generic interfaces call out the rear O2 sensor’s contribution to fuel trim separately under a heading such as FTB1S2.) "
Unfortunately there is very little information about this topic - at least that I could find. I'd certainly like to know more about this.
reading volume one FSM 2007 extensively, best I can say is that I would bet against the rear sensors having anything to do with lambda.
now... I'm not sure I'd say the same about any other years besides the 06-7. I"d guess the same, but who really knows.
IF you drill down the chart for 420 and 30 in a vvti car you might come to the same conclusion, depends.
The narrow band response rate can be up to 20 seconds, from the book.
That article linked has good info in it, it's just old. He writes like he never saw an air fuel sensor before 2010.
now... I'm not sure I'd say the same about any other years besides the 06-7. I"d guess the same, but who really knows.
IF you drill down the chart for 420 and 30 in a vvti car you might come to the same conclusion, depends.
The narrow band response rate can be up to 20 seconds, from the book.
That article linked has good info in it, it's just old. He writes like he never saw an air fuel sensor before 2010.
Searched through some of the Toyota/Lexus technician's training material. Only found one reference to this in Tech Training L852, chapter 8:
Fuel control by the sub O2 sensor is a very fine adjustment. Its affect on fuel trim and driveability is extremely limited.
So how fine? According to this post on IH8MUD the 80 series engine management allows for +/-2% fine tuning based on the rear O2 sensors. Some more reference to 2% can be found here.
From training L874:
The sub (S2) O2 sensor is used to adjust the oxygen level in the catalytic converter to achieve the best catalytic converter efficiency possible. As a catalytic converter deteriorates, its ability to store oxygen is also reduced. During conversion, the stored oxygen is rapidly depleted. The sub O2 sensor detects this and, within a very limited range, the ECM will reduce the amount of fuel injected providing more oxygen to converter. Oxygen levels build up, driving the O2 signal downward. At a predetermined point, fuel control will return to stoichiometric A/F Ratio. When this happens, oxygen again will be depleted driving the sub O2 signal upward, and the cycle will repeat itself. The rate at which this cycle repeats depends on how much of the catalyst has deteriorated, engine load, and the amount of correction as determined by the ECM's fuel control programming.
Fuel control by the sub O2 sensor is a very fine adjustment. Its affect on fuel trim and driveability is extremely limited.
So how fine? According to this post on IH8MUD the 80 series engine management allows for +/-2% fine tuning based on the rear O2 sensors. Some more reference to 2% can be found here.
From training L874:
The sub (S2) O2 sensor is used to adjust the oxygen level in the catalytic converter to achieve the best catalytic converter efficiency possible. As a catalytic converter deteriorates, its ability to store oxygen is also reduced. During conversion, the stored oxygen is rapidly depleted. The sub O2 sensor detects this and, within a very limited range, the ECM will reduce the amount of fuel injected providing more oxygen to converter. Oxygen levels build up, driving the O2 signal downward. At a predetermined point, fuel control will return to stoichiometric A/F Ratio. When this happens, oxygen again will be depleted driving the sub O2 signal upward, and the cycle will repeat itself. The rate at which this cycle repeats depends on how much of the catalyst has deteriorated, engine load, and the amount of correction as determined by the ECM's fuel control programming.
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- Thread starter
- #12
I replaced all 4 of the 02 sensors as PM. It could be my imagination, but it seems like power delivery and shifting is much smoother now, particularly when going up steep hills.
Anyway, it may have been unnecessary but it's one less thing to worry about
Anyway, it may have been unnecessary but it's one less thing to worry about
