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Advice requested for how to handle my 1st P0133 slow response O2 sensor on a '97 2.7L

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Old 02-11-2013, 02:02 PM   #1
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Advice requested for how to handle my 1st P0133 slow response O2 sensor on a '97 2.7L

My first post on this forum so please guide me if/when I err.

Kid's 4 cylinder Toyota 2.7L 1997 4Runner 2WD with 133K miles triggered an SES today.
My code reader indicates P0133 only.
Googling implicates "Oxygen Sensor Circuit Slow Response (Bank 1, Sensor 1)"
A description appears to be:
Quote:
P0133 means the upstream oxygen sensor on bank one is not responding as quickly as it should to changes in oxygen levels in the exhaust.

The usual causes of this is an oxygen sensor that is worn out or contaminated.
The original oxygen sensors were never replaced to our knowledge. We have a small oil leak coming either from the oil pan or oil filter bracket mating surfaces to the engine.

We have the factory shop manual and the Chilton manual - but we have never worked on an oxygen sensor so we ask advice before we tackle this job.

Q1: Do you think an oil leak at the locations above can contaminate an 02 sensor?
Q2: Do you generally remove them in pairs?
Q3: Any other advice for diagnostic tests?

Note: We will continue googling - so this is one step in our quest.



EDIT:
Found section 4-9 in the Chilton manual which explained oxygen sensor behavior; they mentioned a "backprobe" for voltage, which I assume is we nick the wire insulation somehow. Any advice on how to "backprobe".

Also we looked on the passenger side for the oxygen sensor and wire. Maybe it's under the shield? Do these pictures show it to you?
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Old 02-12-2013, 05:58 AM   #2
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I had the same callout. Replaced both sensors but it turned out to be the egr solenoid. (I think). My mechanic buddy did it because it was kicking my butt after I had replaced both sensors.
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Old 02-12-2013, 06:37 AM   #3
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I dont have any input on your question, but damn! Your engine is clean - particularly your valve cover. Do you do anything in particular to clean your engine bay?
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Old 02-12-2013, 06:54 AM   #4
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I would start with taking some measurements to see if the sensors are in spec still. Backprobing is when you take a meter lead and stick it in the back of the connector. They also make little prongs that you can push past the weather tight seals and they stay in place. This makes it easy for quick reading while you are diagnosing.
As for the EGR valve being bad and throwing an o2 code, not possible. They are different circuits and unrelated to each other. O2 sensors merely measure your air/fuel mixture. An EGR recirculates exhaust gases for emissions stuff. At least I don't think it it possible and I have never seen a bad EGR come up with a o2 code. o2's do go bad though. The computer wants it to read and fluctuate faster to keep a more consistent a/f mix. If it is slow to do this then the computer may go into closed loop all the time and run off base parameters. This will cause loss of mpg's.

To Moco,
If you want to degrease your engine bay of grime, use oven cleaner. Just spray it on all the greasy spots. Let it sit for a few min and wash it off.
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Old 02-12-2013, 08:05 AM   #5
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Quote:
Originally Posted by Moco View Post
Do you do anything in particular to clean your engine bay?
As I had mentioned in the OP, there is an oil leak of the oil pan or oil filter bracket mating surface to the engine - so - I had used gunk on the engine about a month or so ago.

Quote:
Originally Posted by ntilehman View Post
I would start with taking some measurements to see if the sensors are in spec still.
Exactly what I plan on doing (as I don't just throw parts at a problem) - so the question is what measurements & how.

Googling, I find the attached 500-page Toyota 3RXZ-FE diagnostic manual and also, surprisingly, an o2 sensor diagnostic sequence at Autozone.

Quote:
Originally Posted by ntilehman View Post
Backprobing is when you take a meter lead and stick it in the back of the connector.
Ah good. I was afraid I'd have to puncture the insulation. I have a good DMM so now I just have to read up a bit more on how to test the forward oxygen sensor in situ.

I found this Ehow DIY (sans photos, unfortunately):
- How to Replace an O2 Sensor on a 1997 Toyota 4Runner

Where do you guys normally get your electronic sensors from?
Is this a dealer-only part, or can the Denso online guys source it for me?
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File Type: pdf toyota_4runner_tacoma_3rz-fe_engine_diagnostic_tree.pdf (2.30 MB, 416 views)
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Old 02-12-2013, 01:00 PM   #6
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Quote:
Originally Posted by ntilehman View Post
Backprobing is when you take a meter lead and stick it in the back of the connector.
Trying again (the last post said it awaited moderator approval ... dunno why.)

Looking in the Toyota FSM (page SF-36), all it says is the resistance should be 11 ohms to 16 ohms between the connector pins +B and HT, so I'll need to do some more research for values.

I crawled under and found the sensor to be very easy to access - but I couldn't figure out how to disconnect the diabolical harness connector. It had one "ear" clip that I pressed - but there must be another one holding the connector in place.
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Old 02-12-2013, 01:05 PM   #7
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Quote:
Originally Posted by Aquatic Tacoma View Post
Replaced both sensors but it turned out to be
Wow. At the $213 the dealer wants or the prices below at Autozone, it's darn expensive to replace BOTH without testing them first.

The Chilton manual has a test procedure to run where I can backprobe to test the voltage fluctuations, so that's the next step - although I was surprised that clearing the codes and driving a bit less than 100 miles didn't trigger even a pending code return. Hmmmm???

Anyway, the prices seem to be around $90 to $110 (for Denso) at Autozone but I wonder HOW to choose between the various options? Any suggestions as to how to pick oxygen sensors?



EDIT: I called Autozone and they told me the cheaper ones are the "universal" oxygen sensors (both Bosch & Denso) where you have to splice the wires yourself.
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Old 02-12-2013, 02:05 PM   #8
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get o2 bung spacers. 14 dollar fix. getting to much air flow. IMO
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Old 02-13-2013, 10:14 AM   #9
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Quote:
Originally Posted by Hambone155 View Post
get o2 bung spacers. 14 dollar fix. getting to much air flow. IMO
I must admit I had to look up the bung spacers.
Apparently they physically move the oxygen sensor further away from the exhaust flow.
But they seem to mostly be for P0420 & P0120 DTC codes, from my quick search, not P0133.

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Old 02-13-2013, 10:36 AM   #10
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Quote:
Originally Posted by Hambone155 View Post
get o2 bung spacers. 14 dollar fix. getting to much air flow. IMO
Quote:
Originally Posted by RockSockDoc View Post
I must admit I had to look up the bung spacers.
Apparently they physically move the oxygen sensor further away from the exhaust flow.
But they seem to mostly be for P0420 & P0120 DTC codes, from my quick search, not P0133.


The "bungs" mentioned are used to move the O2 sensor out of the flow of exhaust. This simply fools the post-cat O2 sensors into believing the catalytic converter is working properly. While this does reduce the chances of a P0420 from returning, it would not fix the problem. It simply masks it.

If you were to use those bungs on the pre-cat sensor(s), you would most likely result in creating a code, instead of eliminating it. Moving the AF sensor out of the exhaust stream will make the sensor read no changes, and the computer expects to see a steady fluctuation of the signal. (hence the P0133 code for a slow response)

A bad EGR valve can cause a p0133 code however, because if it leaks, it allows recirculation of the exhaust gases when the computer is not wanting, nor expecting it. This can cause a flat signal of the AF sensor, and a resulting P0133. If you have a scanner that can give you basic data, you should be able to observe the AF sensor data, as well as fuel trim data, to see if you have a problem elsewhere, that is triggering the code. Fuel trim codes on a Toyota do not occur until close to 25% in change, so if you were running lean, or rich, you would not get a fuel trim code unless it was severe enough to take it past the 25% range. So look at all of the data. AF sensor, fuel trim (both long and short term), EGR command, etc. If the code is a history code, and is not a result of EGR or fuel trim issues, then you may be able to go to your local parts place and purchase O2 sensor cleaner, and just remove and clean the sensor. Considering the cost of a replacement, a $5.00 can of cleaner to at least TRY to resolve the problem is not a bad idea. Again though, check the data first and see if the code is a failure, or the result of another problem.
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Old 02-15-2013, 08:38 AM   #11
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Quote:
Originally Posted by BamaToy1997
The "bungs" mentioned ...simply fools the post-cat O2 sensors into believing the catalytic converter is working properly.
Thank you very much for the additional explanation - as the entire bung idea was wholly new to me.

As you intimated, I'd rather identify and fix the problem than try to beat it with the bungs.

Quote:
Originally Posted by BamaToy1997
look at all of the data. AF sensor, fuel trim (both long and short term), EGR command, etc.
Thanks for the good idea and the rationale behind it (which is just as important).

Unfortunately, the scanner I have doesn't do freeze frame so I need a better scanner to obtain that data. I always wondered if it was useful - and - apparently - in this case - it would be useful to have.

Quote:
Originally Posted by BamaToy1997
a $5.00 can of cleaner to at least TRY to resolve the problem is not a bad idea. .
Interesting. I had not realized that an oxygen sensor 'could' be cleaned. But it makes sense if getting dirty is the reason for a failure - then cleaning it should work.

Googling, this "ehow" (yeah, I know) article says you can clean an o2 sensor in gasoline overnight.
http://www.ehow.com/how_4797809_clea...n-sensors.html

However, this discussion goes into how the "baked carbon" is what you really need to solubilize:
http://www.ford-trucks.com/forums/60...en-sensor.html
Quote:
It's not whether an o2 sensor can or can't be cleaned. Anything can be cleaned, if you go about it right.

The question should be, first of all, whether cleaning it would do any good, and if so, whether it needs to be cleaned.

Oxygen sensors are exposed to such extreme heat that the only thing that it can get (dirty) with is carbon. Extreme heat will turn any organic matter, such as gasoline or oil, into carbon. Well the bad thing about that, is that baked carbon is not soluble in any kind of solvent, and even if it was, the sensing unit within the o2 sensor module, is not exposed, and is not visible.

It is covered by what is usually a louvered steel cylinder. Therefor if you're going to brush it, use a wire brush and brush it as hard as you want, because it isn't going to hurt the steel cover. But this is the problem. The only thing that you can really clean with any success is the outer cover.

Since solvents won't do any good, I really would not recomend using electric motor cleaner, since the active indredient in it is Trichloroethylene which is not a very strong solvent. not only is its strength very low, but also, since it is designed to clean electronic components, it evaporates very rapidly, resulting in a very short working time.

Since o2 sensors are designed to handle such extreme temperatures. The best method of cleaning them, is to heat the bottom part of the sensor (the part that inserts into the exhaust) with a propane torch, to the point that it just begins to turn red.

You do not want it to glow cherry red, even though they are designed to take extreme heat, you can still over do it. Once you have it heated to the point that is just turns red, or to the point just before it turns red, quench it in water. This will break free any carbon build up inside the sensor. After the first time, some pieces may still be to big to come out of the sensor so I would recommend doing it 2 to 3 times, blowing it out with an air compressor between each time.

But I would have to say, good luck, since O2 sensors very seldom fail do to being dirty. This is not common at all.
Quote:
It is generally not a good idea to use water to clean O2 sensors. Sudden cooling hot Sensors (heat-tempering) also runs the risk of cracking them. The sensor uses ceramic components. These components are more durable than the ceramic you'd expect to find on your sparkplugs, but still they're just colored glass.

Cleaning is not a bad idea, but it's difficult to get it clean enough to make any difference. Try blowing loose soot out with compressed air. Solvent might work, or might move the soot further into the sensor and deposit it there when the solvent evaporates.
Quote:
The threads on the sensor are only good for so many times in and out.... When you replace the sensor, you get a clean set of threads.

Second issue, the heated part that extends into the engine is not the only part of the sensor that needs t be cleaned. The sensor allows air to enter near where the wires come in on the outside of the sensor. The sensor measures the O2 content of the exhaust relative to the ambient level. You cannot get to either the ambient part of the sensor, nor the exhaust part directly, as they are both shielded. So effectively cleaning them is very difficult if not impossible.

Another point to consider. If cleaning sensors was practical and cost effective...then you would be able to purchase remanufactured O2 sensors. The fact that no remanufactured O2 sensors are available means that no one has figured out a way to fully restore an O2 sensor that is cheaper than just replacing it.
Quote:
An OX sensor is based on a ceramic substrate and depends on oxygen "migration" through the substrate to generate a voltage for feedback to the PCM in proportion to what it finds in the exhaust flow.
It normally must operate at exhaust temperatures in excess of 600° to output it's intended varying voltage for the PCM to use.
Two major types of conditions could exist.

One, a crusting from combustion deposits as a result of what's in various gasolines
.
Secondly, deposits from cylinders burning oil in the combustion mix, or coolant leaking into the combustion process or some other contaminant introduced through the intake.

For the crusting, heating tip area with a torch to burn off the deposits often will bring back sufficient operation as detected on a digital voltmeter monitoring the sensor output as the tip is heated to a dull red color.

Much of the time the tip has a metal guard over the sensor areas and you can't see the actual active area.

If some other contaminant is present like oil, the substrate may be block beyond cleaning by any method.

Attempts to clean with various cleaners may render a unit inoperable or slow laxly operation by blocking the substrate and you would never know this.

So the answer to the question of cleaning is, "it depends".

Don't use any cleaners. You are often warned not to introduce anything ahead of the sensors, not to use certain additives, lubes and greases, gasket sealers etc that may come in contact with the sensors.
Having never before dealt with oxygen sensors, I'm just coming up to speed. At over $200 at the dealer, it makes sense to clean them - yet - at over $100 at the autoparts store, it still makes sense to try - yet- at around $60 on Amazon, it might only be worth it if I have the part already in hand, as a last-ditch effort:
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Old 02-15-2013, 08:48 AM   #12
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Found s'more information about cleaning oxygen sensors here:
http://ls1tech.com/forums/conversion...s-cleaned.html

Quote:
There are essentially 2 types of narrow band oxygen sensors using either titania or zirconia ceramics (generally these ceramics are actually doped with other elements.) The ones you generally deal with are zirconia.

The short answer is no, they generally can't be cleaned.

The long answer:
There are a couple failure models
1. Broken wires
2. Broken heater circuits
3. Damaged/cracked ceramic
4. Eroded ceramic (hot exhaust gasses plus tiny particulates over a long period of time really will just erode the ceramic to nothing)
5. Contaminated ceramic

The first four the ECU should pick up as a completely non-functional circuit (and cleaning wouldn't help.) The fifth is the only instance when cleaning may be an option, in this instance generally the ECU will report out that the sensor is having a slow response (low cross count).

Ultrasonic cleaning may be an option, but is likely to damage the ceramic or the electrical attachments.

The other popular option is soaking the sensor tip in gasoline. If the contaminant were soluble in gasoline (typically it isn't), then this could theoretically clean the sensor, but the ceramic is a somewhat porous structure and the contaminants become embedded in the sensor, making it questionable if the solvent would do a reasonable job.

Incidentally the metal you see is not the sensor itself, just a protective shell. Physical agitation on the sensor itself would likely destroy it.

Lot of effort to slightly lengthen the life of the sensor, and it probably won't work. So generally if a sensor goes it is simply replaced, they aren't THAT expensive.

Common contaminants:
a. Silicone from sealants, are soluble in gasoline
b. Soots, occasionally soluble in gasoline
c. Glycols, insoluble in gasoline
d. Metal contamination, insoluble in gasoline
e. Oil addatives, generally insoluble in gasoline (often metals, silica, potassium, calcium, etc.)

If you are curious why that test won't work with a Titania sensor, it is because they are actually powered and the O2 concentration on either side changes the resistance, as opposed to Zirconia which actually develops a voltage based on the O2 concentration imbalance. Oh, and wideband lambda sensors are a completely different beast.
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