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940 how to measure O2 signal for regina?

thelostartof

thelostartof

unbalanced chemical
300+ Club
Joined
Jun 26, 2002
Location
Apache Junction, AZ
Car is a 1993 944 with Regina. Would any of the said experts here be able to tell me how to measure the O2 output on my Regina car and what scale I should be looking at to validate the signal?

When I redo my header this week from 4-2-1 to a 4-1 Iam planning on adding a ssecond O2 port so I can connect my spare wideband to be 100% sure but for now I figured after 7+ years of driving Regina cars it would be finally nice to be able to know how to read the O2 output. I know which wire I just need to know what scale and what to set my meter on.
Thanks
 
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http://www.autoshop101.com/forms/h37.pdf

look for 150mV to 750mV *SWING* in the readings...sustained high or low
readings indicate a sensor / mixture problem....

the above pdf includes the Zirconia (narrow) and Titania (wide) band HEATED
sensors....the second one in the system is appropriately called the AIR/FUEL
RATION sensor and is used as a COMPARATOR in conjunction with the
signal from the "lead / narrow band" sensor in front of the cats...DTC for
"Cat Convertor Efficiency BELOW THRESHOLD" comes from this
comparison.....
 
That document says that it should be resistance not Volts.

I know a normal O2 will swing from .2-.8 V, Mine used to typically sit around .4-.6 at idle back when I had a narrow band gauge.

So if resistance I should set my meter on Ohms? or mV?
 
The zirconia (Bosch) and titania (Regina) sensors used in our Volvos are both narrowband. True, the zirconia sensor is solid electrolyte battery generating a voltage while the titania sensor varies its resistance. The Regina sensor requires an external current source to map its output voltage to a similar range for the ECU to find stoich at about 0.5V, so if you disconnect the sensor from the ECU, it will look just like a variable resistor dependent on oxygen content when heated, unlike the zirconia which actually generates the voltage.

Measure it just like you do the Bosch, in circuit and closed loop, looking for switching around the 1/2-volt point, but because the resistance is lower when rich, I believe the Regina actually reports in the opposite polarity from that of the Bosch -- explaining why folks have absolutely no luck at all when they try to get away with a cheap Zirconia in the Regina. Sorry, that part of this response is conjecture on my part as the one Regina car I had any fun with (tank pump) is long out of my reach. I'm pretty sure the voltage varies between 0 and 1.1V in Volvo's Regina system, but of course that range is entirely dependent on the ECU's current source.
 
thelostartof said:
So if resistance I should set my meter on Ohms? or mV?
Click to expand...

If I were to measure, I would measure voltage output side (sensor return voltage) if you have a high impedance voltmeter.

Tidbits

Titania sensors use a different type of ceramic and instead of generating a voltage signal that changes with the air/fuel ratio, the sensor's electrical resistance changes. The resistance is less than 1000 ohms when the air/fuel ratio is rich, and more than 20,000 ohms when the air/fuel ratio is lean. The ECU provides a base reference voltage and then rmonitors the sensor return voltage as the sensor's resistance changes.Titania O2 sensors are used on less than 1%of O2 sensor-equipped vehicles:

  • '86-'93 Nissan 3.0L trucks
  • '91-'94 Nissan 3.0L Maxima, 2.0L Sentra
  • '87-'90 Jeep Cherokee, Wrangler, and Eagle Summit


Like the zirconia sensor, this type is nonlinear, such that it is sometimes simplistically described as a binary indicator, reading either "rich" or "lean". Titania sensors are more expensive than zirconia sensors, but they also respond faster.
 
thelostartof said:
So I have a semi fancy Fluke Meter so I am still lost as to what I might set my meter on..
Click to expand...

Volts....you can measure the reference voltage (sensor input side), or sensor's output side, in mV.

If you read 12 Volts, you have connected to sensor's heater voltage...if you always see around 1 Volt always, you have tapped into reference voltage...if you see mV fluctuates, you have found the right wire.
 
thelostartof said:
So I have a semi fancy Fluke Meter so I am still lost as to what I might set my meter on.

This is why I have been putting off on asking.
Click to expand...

Use it just like you would for a Bosch. Keep in mind, using a digital meter to monitor the oxygen sensor is a shade tree method, sort of like using your cell phone camera to capture the events of a football game. Not the right tool, but the one you have...
 
I will know for sure when I get back home and see. I will also try to get some video of what the readout says when running.

The meter can do way more than my little brain knows how to do with it.
 
Here is a quick short crappy video of output on mV, tell me what I am doing wrong and then I will say to bad wait as I have the manifold off and all cut up as I am going from 4-2-1 -> 4-1 along with installing a new cat, the old cat was only showing a 50deg temp difference after a 45 min drive.

<iframe width="420" height="315" src="//www.youtube.com/embed/hiLofjXBTcs" frameborder="0" allowfullscreen></iframe>
 
thelostartof said:
video of output on mV
Click to expand...

One needs a solid ground...ideally, where ECU is grounded.

Did you try the Volt range, instead of mV? I'm not familiar with Flutes...are they auto-ranging? If so, if voltage ranges from mV to Volt readings, that may be why the OL exists.

If OL true, an inline resister on your probe might drop down the one volt readings so you could see a skewed reading.

Is this an old or newer O2 sensor?
 
This is an old O2 sensor, well 2 years old but when I pulled it out it was black black black, pretty bad from running rich.

When I pressure tested the car a few days ago I found a few huge pressure leaks (throttle body adapter was leaking really bad along with brake booster hose and Map hose and fitting to manifold. I fixed all of those and drove the car for the last few days and it felt good. MPG is a solid 23-24 mpg mixed driving (mostly highway) and that is with the lockup converter not working (it randomly locks and unlocks as it wants to). That is crusing @ 70mph, if it drop it down to 65mph I get around 27mpg highway.

Either way the car failed smog running stupid rich along with way high on nox and HC (which are from running rich and the cat not working from running rich for to long). Nevermind that a few months ago my Mother drove the car around 40 miles on the highway @ 5500rpm in 2nd gear because whatever lame excuse older people use, So that caused who knows what other issues as the thin layer of RTV I used on Valve cover gasket melted out along with the timing covers also melted a bit. No idea if the car overheated as she has no idea if it did at the time or not. It still runs nice and smooth so I am not super worried about it.

I did timing belt, plugs, and fixed all of the pressure/vac leaks last weekend so once I get the new cat in place along with redone header and new 02 sensor (along with extra bung so I can throw my wideband in just because) I will be able to try again to see how it goes.

I am so ready to Either MS this car, Go LH or just drop the $ and swap in an LSx engine and be done with the car as if it Gets LH or MS it will also get a turbo.
 
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