O2 Sensor

Actually, that should be 0.1 to 0.9 volts. A healthy O2 sensor will switch
very rapidly - much faster than the scan rate of any DVOM I have seen. This
can and will "cloud" your readings making a lazy O2 look good or making a
good sensor look bad. Be sure that there are no exhaust leaks upstream from
the sensor before you get too far.

The upstream sensor is the one that takes the beating (for the sake of
argument, O2s are considered "sacrificial" parts) while the main job of the
downstream sensor is to monitor catalytic convertor efficiency.

While we're on the subject of multimeters be sure to use a decent DVOM.
Analogue meters (the kind with the needle) have a very low input impedence
(typically 1Meg-ohm per volt) compared to digital meters (typically
10Meg-ohm per volt). The analogue meter can draw enough current to toast
your ECM.

The sensor itself can be very hard to get out. Having the exhaust "hot"
seems to work best in my experience.

Good luck,

--
Jim Warman

If you have a digital voltmeter such as one from Radio Shack in the
$30- range you can check the sensor 'working element' to verify that
it is putting out a slowly varying voltage between 0.1 and 0.3 volts
dc. The 'heating element' of course is NOT what you want to monitor so
check color codes from manual. Clipping into the sensor leads to make
good contact is not easy. If you can grab a bad sensor from the trash
that uses the same connector, and also steal a connector from a wiring
harness in a junker (same year & same engine) you then have the
makings of a nice O2 sensor tester for your particular vehicle. Add
about 15 feet of wire to get inside and you can drive around while you
monitor the voltage. You will spot the bad sensor(s) since they will
exhibit slower voltage dynamics ('lazy sensor syndrome') or will be
just 'flat-liners'. Keep in mind that this voltage output from O2
sensors is always the same, no matter what the engine or manufacturer.
All the elements are made of the same 'rare earth alloys' and exhaust
gases from a gas engine are always the same, too. Only configurations
vary: heater, no heater, return thru ground or thru separate wire, and
choice of connector style. So it ain't rocket science, you just have
to get connected to the 'working element' which is always a 2-pole
device, and read the miniscule voltage off of it.
--
sp
~~~~~~~

Sure you can replace them youself. I diid. However, which one is bad?
your vehicle can have up to four 02 sensors like mine, two upstream
and two downstream. The DTC code are specific to the faulty sensor or
circuit.

Sweet. No wonder the mechanic was so free in sharin' info. All he said was
right sensor. Oh well
Thanks for the feedback,
~OC~

...

"Jim & Debb Warman" <
Yes, I couldn't remember if it was under 0.5 or 1.0v. My meter seemed
to track the variations well enough to at least show it was working
within the required range. As opposed to a 'bad' sensor which would
not do much of anything. A lazy sensor will throw on the 'check
engine' light for a minute or so, and then turn it off (92 Sable). So
I've never had to monitor the voltage of a lazy one. I'm guessing you
should be able to spot some sort of difference from those bad boys.

Upstream/downstream- too new for my fleet!

Like heated red hot with an oxy-acetalene torch!

--
sp
~~~~

well, this has been a very informative thread so far. i just purchased a set
of 4) o2 sensors for my '00 windstar, and was questioned what the
calibration code sticker said.

what difference does the calibration code do? between california emission
cars and the other 49 states?

parker

The calibration sticker is on the driver's door frame It identifies
the engine year, calibration design, and design revision. These
numbers are used to identify service parts and engine specifications
that make up the emission system designed for that vehicle and the
region it operates in.

you brought up another problem i have.

i've got a '95 p/u, and a '97 taurus. on both vehicles i can locate the
white calibration sticker. on the p/u the sticker is on a door jam, and on
the taurus its on the underside of the hood.

now, where are the stickers on newer cars? on my '00 windstar and '02
explorer i cannot find it! is the calibration code integrated into the
identification sticker (lists build date, tire size, vin, etc.)? i also know
of the sticker under the hood (on the radiator support) that lists the
engine size, spark plug gap, etc. i see what looks like ford p/n codes in
small print on it too. but nothing that clearly states "calibration."

my parts guy seemed upset at me for not finding it. asked for my vin and
tracked down my needed o2 sensors, however i'm worried that they may be
incorrect ones.

parker

...

I'm not entirely sure that the calibration code will be required for most of
the parts you'll be getting and certainly not for O2 sensors. Way back when
the '85 pick ups came out with the all new injected 302, the parts dept
would insist on the calibration code, spend 15 minutes furbling around the
microfiche, find out that all the O2 sensors changed up to one of two part
#s. One had a long lead and the other a short one

For the newer ones, I have (thus far) found that the build data available to
the dealer parts dept is very accurate.

--
Jim Warman


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