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!!

 

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')

 

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

 

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!

 

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!!

 

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')

 

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')

 

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

 

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

 

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

 

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

 

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