oxygen (o2) sensor codes S70

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jr - 06 Mar 2005 19:49 GMT

Hi to all,
I was driving the family 1998 S70 (non turbo) and out of the blue the
"check engine" light turns on. I was near an auto parts place that will
retrieve the code. I got two codes. P0133 and P0140. From the time the
light went on to the time the codes were retrieved about 5 minutes of
driving went by. Two codes in five minutes seems a bit odd to me. The
codes point to both different O2 sensors. How likely is it for both O2
sensors to go bad in a five minute period?

I am wondering what are the odds that both of these are valid?
Could one be "sympathic" to the other ?

My searching on the net tells me
P0133 is the front O2 sensor slow response and
P0140 is the rear sensor no activity

A look in the Chiltons manual (all I have, granted not the most
authoritative source of info) tells me P0133 is "front heated O2 sensor
too slow Rear heated O2 sensor compensation"
Chiltons states for the P0140 code "rear heated O2 sensor , check"

I have seen many posts about aftermarket (bosch) vs original, the pros
and cons of splices. Also found some info about "new" originals that
have a "different/improved " wiring arrangement. I would like to know
more about the new wiring arrangement if anyone can provide the details.

I am very much interested in suggestions on the best approach to
figuring this out. Dealer parts seem pretty pricey, direct fit a bit
more reasonable, and splice type least expensive. What I want to avoid
is getting pats I really don't need in the first place.

I also found a bunch of info on vacuum leaks and O2 codes, Best I can
tell this only applies to turbo models. Can anyone verify this please?

Also spotted one post that states it is possible to clean them and
return them to service. Anyone got any experence doing this?

This group has been a great help to me in the past and I very much
appreciate any help.
Thanks
JR

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Mike F - 07 Mar 2005 15:26 GMT

> Hi to all,
> I was driving the family 1998 S70 (non turbo) and out of the blue the
[quoted text clipped - 37 lines]
> Thanks
> JR

Codes and fault tracing are common between turbos and non turbos.
Vacuum leak codes are more likely on turbos because they both stress
their system more (temperature and pressure) as well as having a
somewhat longer and more complicated system.

The new wiring arrangement includes an extension harness which adds a
loop between the engine harness and oxygen sensors, to "prevent
contamination from reaching the oxygen sensor's reference air."

These codes most likely both point to the same problem, most likely
vacuum leaks. However, other things can cause these codes, including
low compression, fuel pressure too low or high, leaks in the exhaust
between the engine and catalytic convertor, as well as one of the oxygen
sensors.

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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jr - 07 Mar 2005 17:06 GMT

>>Hi to all,
>>I was driving the family 1998 S70 (non turbo) and out of the blue the
[quoted text clipped - 52 lines]
> between the engine and catalytic convertor, as well as one of the oxygen
> sensors.

Sounds like I may be busy tracking this down....
I will try the vacuum system first as it sounds like the most likely
cause. The tubing for vacuum looks like 4mm. Are there other common
sizes used in this model car? I don't expect to hear a vacuum leak,
Sounds like outside of getting lucky and actually seeing a defect, I
will be replacing all vacuum hoses. Any individual hoses more likely
than others to start with?

Would leaks in the exhaust system result in a noticable increase in noise?

Should I find the problem, currently I lack a tool to clear the codes,
will the codes clear themselves after some particular amount of driving
or some number of start cycles with out the fault present?

Thanks for the guidance
JR

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Mike F - 08 Mar 2005 13:36 GMT

> Sounds like I may be busy tracking this down....
> I will try the vacuum system first as it sounds like the most likely
[quoted text clipped - 12 lines]
> Thanks for the guidance
> JR

The vacuum hoses are generally plastic pipes, with rubber elbows on each
end to make connections. Usually the rubber elbow deteriorates, and the
problem is obvious. There are a bunch under the plastic cover over the
throttle pulley, and sometimes one at the front end of the intake
manifold behind the power steering pump where it's hard to see.

Exhaust system leaks cause noise, but often someone with a noisy exhaust
won't think there's any possibility that is related to the problem, and
so won't think to mention it.

The light will go off after 3 roughly 30 minute trips after a cold
start, assuming the problem is fixed, at least mine does. However,
vacuum leaks screw up the adaptation, so it may be a good idea to reset
the computer by disconnecting the battery for about 30 minutes. This
will also turn off the light, just be sure to have your radio code
handy.

Signature

Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

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