Oxygen Sensors when to change??

I have a 2004 Sebring Touring 2.7L with almost 100 000kms (60 000miles). Gas mileage has suffered recently. Check Engine light has been on and I have
scanned it...
I have an OBDII error code of 0137. Am I correct that is the oxygen sensor on the driver's side of the tail pipe that is faulty?
I'm taking the car in to have a tyranny flush and new serpentine belt done, should I just have the dealer replace all 4 Oxygen sensors or replace the faulty one. The cost of the oxygen sensors is $47 each from the dealer, not including the labor which was half the price from several auto parts dealers in my area.
Would their be any benefits to replacing all 4 oxygen sensors?? I really want to get another 100 I kames (60 K miles) from this car.
Thanks for the input!!
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The Henchman wrote:

It is the downstream sensor on the bank that is the side of the engine that the a.c. compressor is on (opposite side from the power steering pump).

The downstream O2 sensors only monitor catalytic converter health, and are not in the closed loop engine controls like the upstream sensors are. So that one sensor would not affect fuel mileage. However, the upstream sensors *could* be causing poor mileage without setting a code, but they aren't necessarily the cause of the poor mileage.
FYI - my daily driver is a Concorde with the same engine in it - it has 190k miles on it and is on the original O2 sensors, and gets 26 to 28 mpg on my 80 mile daily commute (gets over 30 mpg on continuous interstate driving). And the Concorde is a much heavier car. BUT - something is causing your poor mileage - could be the O2 sensors, but not necessarily. So it would be a gamble either way.
Maybe someone else can offer ideas on how to rule them out as the cause of the poor mileage, or whether the gamble would be in your favor by just going ahead and replacing them all. BTW - *DO* get the sensros from the dealer. While there are some good sensors in aftermarket, unless you know which brands are the good ones, you're likely to get really bad ones - even among some respected name brands (hint - Bosch no good, NGK are good). If you do go aftermarket, make sure you get ones that come with the factory-type connectors already installed, otherwise you would have some splicing to do.
As long as you religiously change the oil at less than 4000 mile intervals, you should be able to get another 60k miles out of the engine. Like I said - I'm at 190k miles and running strong (however, I do need new exhaust valve seals, which do tend to typically be required somewhere beyond 110k miles on this engine, and manifest themselves in a code that says the catalytic converter is not working efficiently - code P0420 or P0432, which means the catalytic converter is shot due to too much oil in the exhaust).
As you may know, this engine has a timing chain instead of a belt, so there is no change interval on that. HOWEVER, the water pump is run by the chain, and the pumps have been known to fail.

You're welcome!
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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have
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done,
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not
dealers
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Not true. The first purpose of the downstream 02 sensor is to measure cat efficiency. The second function is downstream fuel control. This function adjusts the upstream 02 goal voltage within the range of operation of the upstream sensor. The upstream goal voltage is used to ensure long cat life by allowing the pcm to control the amount of air and fuel that is supplied to the cat. If the downstream 02 sensor switch point is at a low voltage the Pcm will adjust the upstream 02 goal voltage to reduce high 02 content by . If the downstream 02 sensor switch points stays high, the upstream 02 sensor goal voltage will change and allow a low 02 content.
Glenn Beasley Chrysler Tech
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I don't get it. There are two downstream sensors are there not? Does the downstream sensor on the drivers side control the bank 1 sensor on the exhaust manifold and the passenger side sesnor talk to the bank 2 sensor on the manifold? Is there a map as to how these sensors talk to each other. One of them are giving me a low voltage error thants all I know. All cars I had before now I would change the sensors at 100 K km (60 000 mile odometer) read.
I got to take this car intot he delaer for a 100 K km tune-up. Should i be spending the $200 required to change all 4 sensors? is this a normal thing? What does low voltage from an O2 sensor mea? What is upstream and what is downstream?
Thanks for all the help and have a great weekend!
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cat
function
life
supplied
voltage
upstream
on
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odometer)
There are (4) 02 sensors on that vehicle. 2 upstream sensors (located before the catalytic converters), one on the left side and one on the right side. And 2 downstream sensors one on the left and one on the right side just past the catalytic converter. The purpose of the up stream sensor is to maintain the proper air fuel mixture. And the downstream sensors are used to make sure the catalytic converters are working. When looking at a scan tool to determine which sensor is where. 1/1 is the upstream sensor on the number cylinder side, 1/2 is the downstream 02 sensor on the #1 cyl side. 2/1 is the upstream sensor on the other head. 2/2 is the downstream sensor on the same head as the 2/1. The p0137 fault is referring to the downstream 02 sensor on the back head past the catalytic converter (it is the downstream sensor rear head) The monitored set condition is (cold start engine, coolant below 98 degrees and ambient temp with 20 degrees of engine temp The fault code will set if the 02 signal volts is below .059 volts for 3 seconds after starting the engine. The sensor is shorted to ground either at the sensor or the wire going to the PAM from the sensor is shorted. Best bet would be replacing the (1/2) 02 sensor only.
Glenn Beasley Chrysler Tech
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cat
function
life
supplied
voltage
upstream
on
I
odometer)
There are (4) 02 sensors on that vehicle. 2 upstream sensors (located before the catalytic converters), one on the left side and one on the right side. And 2 downstream sensors one on the left and one on the right side just past the catalytic converter. The purpose of the up stream sensor is to maintain the proper air fuel mixture. And the downstream sensors are used to make sure the catalytic converters are working. When looking at a scan tool to determine which sensor is where. 1/1 is the upstream sensor on the number cylinder side, 1/2 is the downstream 02 sensor on the #1 cyl side. 2/1 is the upstream sensor on the other head. 2/2 is the downstream sensor on the same head as the 2/1. The p0137 fault is referring to the downstream 02 sensor on the back head past the catalytic converter (it is the downstream sensor rear head) The monitored set condition is (cold start engine, coolant below 98 degrees and ambient temp with 20 degrees of engine temp The fault code will set if the 02 signal volts is below .059 volts for 3 seconds after starting the engine. The sensor is shorted to ground either at the sensor or the wire going to the PAM from the sensor is shorted. Best bet would be replacing the (1/2) 02 sensor only.
Glenn Beasley Chrysler Tech
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maxpower wrote:

For now, I defer to you on this Glenn. I had read thru the description of the O2 sensor operation several times in the FSM (though I know they don't always tell the whole story), and forums that I have read that it is discussed on, it is stated like I said. I will re-investigate and report back. But you're probably right.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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cat
function
the
life
supplied
voltage
content
upstream
The factory service manual does not get into details as our student handbooks do. I save every book I get and refer back to them on many occasions. When I read this post it brought back some of the stuff we talked about in class long ago.
Glenn
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cat
function
the
life
supplied
voltage
content
upstream
The factory service manual does not get into details as our student handbooks do. I save every book I get and refer back to them on many occasions. When I read this post it brought back some of the stuff we talked about in class long ago.
Glenn
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I was planning on replacing the "fan belt" not the timing chain. Sorry for the confusion.
I am getting a rich air-fuel mixture and exhaust as I had idling issues after long freeway runs for about 3 weeks just before the check engine light came on. Those idling issues are gone HOWEVER now I notice I have a richer exhaust if you judge by the white condensation coming out of my tailpipe and it takes much longer for the engine to warm up. Engine warming up is really important here in Canada cause I need to get my cabin warm LOL.
What are your thoughts? Do people replace the O2 sensors on these cars regularly?
Also where is the PCV??? I need to replace that.
Thanks for all the help!!
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The Henchman wrote:

You didn't confuse me. I was just offering that info. on the timing chain (vs. belt) (along with my ongoing 2.7L experience as encouragement) in case you weren't aware of it due to your mention of your intention of getting more life out of it - I had not even noticed your previous mention of the serpentine belt until now.

No - only if they are suspect or actually failing.

Located on top of intake plenum - connects to hose that comes from valve cover. I advise getting that item from the dealer (some aftermarket parts are suspect).

You're welcome.
From your post immediately preceding this one: "What is upstream and what is downstream?" Same terminology used in rivers and creeks. Each side of the engine has two O2 sensors - one precedes (is 'upstream' of) the catalytic converter, the other one is after ('downstream' of) the catalytic converter.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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have
sensor
done,
not
dealers
Yes - O2 sensors are like light bulbs they wear out over time. 60K miles is around the time that they will start going.
By the time the engine computer has determined an O2 sensor is bad, the sensor has been "lazy" for a while.
-However- it is also possible to check for this. The mechanic can put a oscilloscope (ie: engine analyzer) on each of the sensors and observe the speed of their response to changes in the exhaust stream.
Ask the dealer to quote the job as 1 job replacing all 4 of them, or 4 separate jobs. If the dealer is tacking on a fixed labor charge to each sensor replacement, why then it is going to cost the same to replace all 4 over time, or all 4 at once. Yet, there is labor expended in getting the car into the service bay and on a lift and such - so, there is a slight savings in labor to do all at one time. If the dealer is willing to pass that cost along to you - it might make sense to get them all done now.
You might also ask if the O2 sensor is covered under the federally-mandated emissions warranty. Seems to me that it should be.
Ted
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