Hey Rrich. Really I need to adjust my writing so it's easier to understand. When I installed the new, the needle wavered right over 2-1/2 volts, which is what had I hoped to see. That was on my 90, I believe it's the same part back to at least 87. And yea, Bosch makes them as well, might even be the OEM for Renix. I saw that posted a few times, and that is what (adults), at car quest thought.

"Was it dead BEFORE you put the meter on? How do you know if you did not test it correctly BEFORE you blew it out with the meter?"
I can't debate that! I did leave my jumper on the new one and drive to town and back (1/2 hr each way) with no ill effect that I could see. By what mechanism my meter could blow something that sees a 5 volt feed is unclear to me at this point. Maybe it's like the Kung Foo guy who sets his finger on a brick and it pops in two!

 

I think doing a live reading would be better. Then you're not sending anything through the sensor, you're seeing what is sent from the sensor to the ecu. Trace the wire to the ecu and intercept it with your + lead. Ground the - and fire it up. Then you can see the voltage as it heats up.

 

It's not kung foo.
The sensor is very weak and fragile. It's a chemical reaction that generates the voltage.
Picture a bridge made out of toothpicks - it may look good, but it's very weak. Will it support the weight of the Jeep?

When it reaches temp the voltage jumps from near 0 to near 1 volt. It's constantly switching up and down - called cross counts. It should switch at least once a second - hi to lo.
When it gets old and tired - like me - cross counts drop, even stop.
Using a meter that strains or puts too much load on gives you inaccurate readings and has the distinct possibility of killing the sensor permanently.
The switching from high to lo as the oxygen varies tells the computer if it's rich or lean, allowing it to adjust properly. The computer is looking for the average to be about .5 v.

Testing the sensor
http://www.mr2.com/TEXT/O2_Sensor.html


This should shed some light on WHY you saw 2.5 volts.
http://www.fuelsaver-mpg.com/o2-sensors-types-of

It's the bias voltage provided by the computer.
Disconnect the sensor - it's still there!

When you find your mileage is way too low, keep fouling plugs, burn up your cat from running too rich, and fail emissions tests, you'll realize what you've done.

Try - hooking a high powered speaker 4-8 Ohms (lo impedance) to the earphone jack on a radio 20,000 ohms or higher (high impedance) and see how well it works.

You toss the term RMS around, do you even know what that means?

Root Mean Square!

 

Tank - how does testing it at the other end of the same wire make it any safer?

 

I'm turning the garden today, I'll look over the links better later. The Renix ECU 5 volt feed is being grounded properly to leave the optimum 2-1/2 V (yes pulsing plus and minus). Yes, I even understand a little of what root mean square means. This is a 3 wire sensor you know. More later , and thanks!

 

Because your not forcing voltage through it. One wire is for OUTPUT. You're just watching what the ecu is reading....I said LIVE, right?

Here...

http://expertscolumn.com/content/how-test-oxygen-sensor

 

Tank - you need to learn something about electricity.
You don't "force voltage" through anything.

The voltage will be the same at both ends of the wire no matter what. It' not a high current device where voltage drop is a concern, like a starter cable.

 

Flint -
A quick and simple explanation:
http://www.ngk.com/sparkplug411.asp?kw=Titania&mfid=1

Try something - unhook the sensor from the circuit while still measuring the circuit (harness side.) Still 2.5 volts from the computer!

The voltmeter "loads" the circuit enough that it changes what the computer "sees" and makes it's decisions on.

When the sensor reads from 1,000 ohms to 20,000, putting a low impedance voltmeter in parallel with it makes a huge difference.

ie: if the sensor was reading 10,000 ohms at the time, and you put a 10,000 ohm voltmeter across it, the total resistance is now 5,000 Ohms - that's a completely different input to the computer, so it bases it's AF ratio on that reading. NEXT PROBLEM - since now the computer is now richening or leaning the mixture based on the wrong value, that changes the O2 content in the exhaust, which changes the output of the sensor - now where are you? Now it's distorting based on distortion!

ie #2: If at the time the sensor was reading 20,000 ohms and you put a cheapie 5,000 ohms/volt meter across it - now the effective resistance is 4,000 Ohms, a huge difference from reality. Again it then distorts based on distortion!

Using a meter with over 100,000 Ohms/volt - high impedance - affects it still, but not near as much. It's just simple Ohm's Law.
(R1*R2) / (R1+R2)

Decent analog meters say right on the meter what the resistance is - cheapies don't.

Digital meters are usually very high (like a VTVM) - They tell the internal resistance in the instruction sheet.

The 2.5 Volts is simply a bias voltage. The sensor's variable resistance simply changes that 2.5 slightly up or down, the computer senses these changes and changes it's injection times accordingly.

The best way - a scanner will measure what the computer "thinks" it's seeing - it's an INTERPRETED VALUE. That compensates for any errors or resistances in wiring, grounds, and connections. Plus, since it's reading from the computer's output, the scanner does not load or distort anything.
Older scanners, not OBDII compliant, read the data output easily - those that were more than just a code reader (it's in the Data Stream). We did it for years long before anybody ever heard of OBDII. You see them on EBAY for cheap.

And/or - you can get a data link adapter for your laptop or desktop PC. Then you can get access to lots of data that very few scanners can access. - And they are cheap! Tons of free or nearly free software available to make them work. You can even change some parameters with them!

3 wires on the sensor only shows it has an internal heater - it's not an indicator of sensor type.

 

BTW - I've enjoyed this thread - it's made me recall things I'd long ago forgotten, and I've learned new things - or did I just forget I forgot them?
He He - Oh well, forget it!

I was well on the way to becoming an EE when I got involved with racing and high performance stuff. I ended up owning small businesses and making far more than I would have wearing a tie and a pocket protector. My last shop before I retired was strictly high performance dyno tuning, the most fun!
(You build 'em, we'll make 'em run)

Semi crippled now, cannot do much of anything anymore.

My advice - DON'T GET OLD, I tried it and I hate it!
Golden years? BULL!

 

Is the word apply better? Did that link not work for you, or what?

 

No matter how you say it - the voltage on that low current wire will be the same at both ends.

 

Sigh....obviously. the only reason you do it close to the ecu (read: close to operator) is so you can physically see the your meter when get in your truck, start it, and WATCH what's happening on the readout. Wow. Watching voltage, not measuring resistance....

Still haven't answered my ?'s btw.

 

Rrich, apparently you didn't read my post or somehow you can't get it. Also it seems you do not understand this sensor/system. And for anybody unfortunately trying to follow this mess, No, that GMT 18a meter can in no way damage a titania 02 sensor for A Renix Jeep. I explained that I measured 5 volts on the Jeep side connector FIRST THING IN POST NUMBER ONE!!!!! Coming off gruff and negative, not reading the post, then being wrong, just doesn't help. I'm sure you DO have good stuff we could learn, I would just ask you try to come at it a little more thought out.

Your own link mentions a Titanium Dioxide sensor that subtracts voltage rather than adding it, and uses a 5 volt feed, like the renix.

Hank, on the wire, yea, I just didn't want to dig into the wiring down under the dash. There is a large rubber plug in the firewall (above the fuse-box in the corner there). That wire in the meter there in post one, that wire I routed through the hole to my pig-tale so I could watch the reading while driving.

I would be cautious what I exposed that sensor wire to, but that meter won't hurt it. I went ahead and put a "meter on the meter", showed Zip, Zero, nothing. Too bad, I need to brake some bricks.

 

"""""The 90 Renix ran fine without it. Just bad low speed mileage, idle "seeking", & slow to get to temp"""""

So that isn't true?

Now you say the sensor is NOT connected, but you also said it is!
Which is it?

You saw the voltage fluctuate with the sensor DISCONNECTED? ???? You've read how it works, please explain how that can happen.

What do you THINK you accomplish trying to read a meter with another meter? Sorry, not valid!

The instructions that came with your meter tell what the resistance is. Try reading them.

Obviously you know everything so I won't bother anymore. Just don't get everyone to ruin their senors because you did.

 

If you really want to know the meter's resistance, and don't believe the mfgr, try this:

Hook 2 100kOhm resistors in series with a meter capable of measuring MILLIAMPS. Hook the bottom end to ground, top end to 12 volts, milliammeter in series with it. That makes a simple hi impedance string. Not unlike what your computer does.

Current flow should be about 60 MILLIAMPS. Ohm's LAW 12V/200k

Using Kirchoff's Law the point between the 2 100k resistors should be 1/2 The applied voltage at the top of the string - 6 volts.
Hook your meter to that point and to ground. If it's loading the circuit it will read somewhat less.

Measure the total current through the string now (milliamp meter) with your voltmeter meter hooked up.
Using Ohm's Law calculate total resistance through the string.

Rtot=12v/amps. It will be somewhat less than the 200 k series string.

Subtract the top 100k from that, that gives the bottom portion's total resistance.

Now a little algebra - isolate X, the resistance of the meter.

(100k*X) / 100K + X X=METER'S RESISTANCE - ON THAT SCALE!

Simple!
Or look at your instruction manual for that meter.

I used 12 volts as the example, but any voltage will suffice as long as its constant.
Your Jeep computer does that several times a second.