Check engine light hell

Hi yall,

My wife has a 1999 S70 2.4 (non-turbo) that is really a spiffy car and
she loves it (to date).

A couple of months ago, the check engine light came on...

I went to several auto parts places and pulled codes. Oxygen sensor
bank 1 sensor 1 they said.

Both the stores felt this was the sensor before the catalyst. After
ordering and getting the proper sensor, I installed it and reset the
computer. 10 minutes later, the light is on AGAIN.

So 180 bucks thrown at the sensor was wasted apparently?

Other ideas, or suggestions on how to fix this are appreciated.

 

Visually check the the intake manifold and associated hoses for any
vacuum leaks and correct any found. If none are found (unlikely) have t
someone smoke test the manifold for leaks. Either unmetered air is
reaching the sensor and forcing the system rich or the sensor is bad or
the MAF is sending incorrect data that is forcing the system rich.

What live data long and short term fuel trim numbers did the scan tool
show on the snapshot screen when the DTC was set the last time? What
P0xxx code was set, or better yet what was/is/are the Volvo code(s)?
BTW did you install the extension harness for the HO2S and was it a
factory direct replacement?

Bob

 

I have a 1999 S70 non-turbo as well and the check engine light used to
come on alot as well. So I spent the cash and invested in an OBDII scan
tool. The best money I have spent on this car to date! Every check
engine light since I bought the tool has been due to the bogus gas cap
issue (Gross Evaporative System Failure). It would have cost me almost
$100 CDN per instance to get the code read and the light reset. I could
have waited for the system to cycle through until no code was found but
I don't like doing that as you don't know if something else has gone
wrong. So if I were you I would spend the cash and get the tool. That
way you can read the code and reset the light if need be. Then you can
go either to a dealer or other mechanic with a very good idea of what
is wrong and what needs to be fixed.

My $.02

Jordan B 1999 S70 Loaded!

 

Which one did you get?

 

Thanks for the help! A visual inspection of the intake and hoses show
everything to look ok. no visible or audible leaks. The drivability of
the car is still perfect also.

I went to an autoparts store today and used an OBDII scanner, which now
shows P0136 - O2 Sensor Circuit malfunction (Bank 1 Sensor 2).

This seems odd since I just replaced sensor 1? What are the odds of
them both going bad at the same time?

The replacement was a straight across swap with the original. it took
me four tries at the Auto parts store to get the correct part, but
eventually I got the proper Denso model that looked identical to the
original and had the proper connector also.

Thanks again for any help and or suggestions with this.

 

The code that points to the front O2 sensor in almost any OBDII car (and
probably the OBDI cars, too) means that the sensor is not providing usable
output. That's the rub, since anything that causes the ECU to be unable to
find the correct approximate fuel ratio will set the code.

Think in terms of things like dripping injectors, vacuum leaks, exhaust leak
(but I'd expect you to hear that), MAF sensor adjustment/defect... there are
a fair number of suspects and tracking them down is not always easy. The one
time I had to do that (on my son's misbegotten Taurus... as though there any
Tauruses that aren't misbegotten) I put a scope on the O2 sensor lead and
watched it. The ECU would start at the rich side of the range as shown by
voltage near 1 volt and lean it out to where the sensor transitioned low.
The sensor would vacillate between high and low normally - many times a
second - for a couple seconds and then go high for most of a second. The ECU
tried a leaner mixture and the O2 sensor responded with low output, which
ended when the range sweep ended after maybe 15 seconds. Turned out to be a
dripping throttle body injector that was messing with the mixture.

I expect the new sensor is okay. A close visual inspection of the intake
system sounds like a good (easy) place to start. A fuel pressure test will
tell you if the fuel pressure regulator has gone haywire, and a look at the
plug color should also give you some useful info one way or another. Of
course, a bottle of fuel injector cleaner is cheap, easy, and can't hurt.
Same applies to cleaning the crankcase ventilation system.

Finally, even a digital - not analog because of the loading effect -
voltmeter can tell you something about the O2 sensor operation... although
not as much as a scope can. If you can get the meter between the sensor
output and ground you should read about .45 volt DC when the sensor is
cold - that confirms the connection from the ECU to the sensor. In a few
minutes the voltage should start to change, and (if everything were working
right) you would get a continuous jumble of voltage readings between 0 and
approximately 1 volt. If the voltage does not change from .45 volt, the
sensor is stone dead. If the voltage is around 1 volt most of the time, the
mixture is too rich to start with. If it is around 0 volts most of the time,
the mixture is too lean. In either of those cases, coming off idle should
disturb the status quo and produce a high reading for a moment and a low
reading for a moment, in no particular order. If the reading doesn't change
something is very wrong with the mixture and will probably be visible on the
plugs. If the reading is a jumble as described, the ECU must be complaining
about mixture under some other conditions, like cruise.

Mike

 

maby they diden´t reset the... i down know what the name is i english but
when you switch a oxegen sensor, a MAF some leaking gaskets
you have to do more then reset the error codes. you have to take away a fuse
for 10 minutes in your car it´s one under the hood fuse number 1 or 11 the
name is under the box. it´s 20 amp emmision somthing-

sorry for by bad english

 

Interesting. "they" in this case is me. So I did in fact only reset
the error code from the code scanner...

I pulled the fuse in the "MAIN" fuse box labeled emission for about 15
minutes or so... Do I need to reset the error codes again now? I
suppose so.

No worries, thanks for the help!

 

Ok, I reset it again today and within 10 minutes or so it came back
on. The code it's giving now is the bank 1 sensor 2 code.

Is it likely or possible that both O2 sensors would fail at the same
time? Or is there some known glitch in the OBDII system on this car
that misreports this condition?

I will probably replace the second sensor (the one in the cat), as at
least the error code did change when I replaced the first one?

Any advice on buying these bad boys? I think I will buy a "generic" 4
wire and reuse the old connector? Does anyone here have
recommendations along those lines?

I prefer Denso, as that seems to be factory original and also I hate Bosch ;~)

Thanks for your help.

 

no you don´t hafto reset the error codes after.

 

A bad rear sensor can set a code for the front sensor. The computer
constantly checks and compares the output from the front and rear
sensors and relates those outputs to what it's trying to do to the
mixture. As the sensors (and everything else) wear and get
contaminated, these things all vary, and the computer learns and
compensates. When things get too far enough out of adjustment, it tries
to determine which part is bad, but is not always correct. (Resetting
the codes will reset the compensation, so the computer starts fresh. So
what I always suggest is to always read and reset the codes once and see
what comes back, then start the trouble shooting. However it's always a
bit of a guess when it comes to these things - take comfort in the fact
that both sensors were probably tired so having new ones isn't a bad
thing.

As suggested by someone else, a generic OBD-II code reader can be the
best money you ever spend on this car - especially because OBD-II is a
US government mandated standard, so your reader will work on every other
car from 1996 on.

--
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.)

 

Ok, Thanks very much for this info. I am VERY glad to hear that a
spurious Bank 1 Sensor 1 reading isn't that unusual. Yes, I might
have wasted a couple of hundred on the front sensor, but I am glad to
hear it's not the ECU going wacky on me.

I have ordered a "universal" replacement for the rear (in the cat)
sensor, and should get to that this weekend. Hopefully that will make
the light go off and stay off for a while.

Regarding the OBDII scanner, I personally think buying one is a waste,
as pretty much every auto parts store around here (Seattle) has one to
loan out, for reading and resetting. Also, my cars are all older then
1996, so it wouldn't apply to them.

Thanks a lot for your responses and the very helpful info.

Marty

 

Ok, as of today 2/28/06 the fricking light is finally off.

Apparently the replacement sensor that I wired up and installed is ok,
but the car made a trip to the Volvo dealer anyhow. It had the
"official" code reader connected which didn't provide any additional
info O2 circuit fault bank 1 sensor 2).

However, the trip to the dealer included a reset of the adaptive data,
which seems to have done the trick.

Apparently replacing the O2 sensor is never adequate to make the light
go off. You NEED to clear the adaptive data as well. Pulling the
emissions circuit fuse as I read here isn't adequate.

I can't speak to the disconnection of the battery for 1/2 hour
technique as I didn't try it, and didn't want to find the stupid radio
code. What a waste of time and energy that "feature" is...

Also, I have been told that there is a "software" update that may help
for cars that are stubborn about not wanting to let go of there check
engine lights glow.

I will post back if the light comes on again, otherwise...

Thanks!