(I got allot of my info here> http://www.naxja.org/forum/showthrea...ht=sensor+test)

Edit 1/14. My main goal here was to see how our relatively cheap, high impedance meters cold work checking a "Renix" (that's 1987 to 90), 02 sensors. (the later are very different). Then more comes up!

I was getting 14-16, and a high of 19 MPG, then with the 703's, got'r down to under 11 on one tank.
Unplugged, the Jeep side 02 plug has 12 Volts for the heater (orange on one end). Got the ground down from .9, to .8 ohms by cleaning the ground gang at the dip stick tube. (the ground is in the middle). Then got about 5v on the sensor wire, (other end). All is well. (a note, have the engine running to check the 02 heater wire) .

Then rigged a pigtail, from the 5 Volt sensor wire, plugged it in ran it and got the same, unwavering 5 Volts. It should be wavering over 2-1/2 Volts, or between 1 and 4.
***Edit/added 7/13. What I just said there above is that the Jeep side is fine. The 12v heater power is hot, the 5v from the ECU is fine, and the ground is fine. BUT, that 5v should drop to 1/2 that with it plugged in, running. It didn't drop a bit! (the thing was dead) Ignore Rrich below. He may, or may not have a point on the newer, "Post Renix" 02 sensors. The cheap-o- meter might not be accurate, but it won't "instantly destroy" it. (or damage it)***

It's a safe bet these are not true RMS, and there is no mention of the impedance in the booklets. The large digital was $20 at HF, again I would guess it's high impedance. (Btw, it seems to measure temp accurately)

So, a solid, unwavering 5 volts. Jeep runs great, although the idle slowly cycles, with or without the 02 hooked up.

 

It's on my 90. BOSCH # 12009, NTK #23553, Denso #2343116

 

Drivel deleted !

 

They had the NTK in stock, $69.69, out the door at Car Quest. Hopefully they will spend some money on a handy-man, maybe someday I'll get some of it back!

For a bit, it read the same as above. , Then the needle on the little analog started waving about over about 2-1/2 volts, like it should. Didn't try the digital, had meant to! So that GB Instruments GMT-18A Analog Meter, on the 50 volt DC scale, seems to be suitable to check 02 sensor operation for a Renix. At least it's in the ballpark.
That's back-probing the grey wire, opposite the hot, red 02 heater wire from the 02 heater relay. My center ground wire measured .8 ohms, about the same reading I get connecting my meter leads. (that's after cleaning the ground gang on the dipstick mount),(Cruiser)

It looks like you need the engine running to test the power to the 02 heater. It's relay looks like it's powered by the fuel pump relay.

Misk...On the old sensor, resistance from the HEATER wire to ground is about 12 ohms. It draws about 1/2 an amp, get's hot. (I'm saving that 6 watt, heater/resistor)

Nether grey shows any continuity to ground for me. I held the end the new one in the propane from my stove with no change, except for smelling up the place! I realized later that, that, was "carborated" fuel/AIR mix. ***(being that that that had oxygen in it, I wasn't putting the sensor in propane that WAS free of oxygen)***

The new sensor had 6 ohms from the heater wire to ground, 1/2 of the old one.

The idle seems even now. Was cycling every 30 seconds. Rpm & Vacuum would drop, then a little surge, even out, repeat. Besides the 02 sensor, what I measured was 1/10 of an ohm improvement at the dipstick ground. That's all that was touched.

Here's the link is a link to EcoMikes thread that Slick put me onto, way back! Plenty of info there. http://www.naxja.org/forum/showthrea...ht=sensor+test

Thanks to all. With my foot, I'm gonna get 25 now!

An update 10/13. Got her up to nearly 22 mpg on the highway!(over 275K now)

 

Are you really getting 25mpg from doing all that? I average about 110 miles on 3/4 tank, so anything that can improve my mileage I'll gladly do. As long as it doesn't kill me in the pocket.

 

On the first test drive today I noticed right away, (8-10 minutes), the heater started working! That's all down-hill. It wouldn't kick in before until I hit the first up-hill in 15 minutes. I guess it was rich enough to stay cooler?

My solution to "back-probing" was to strip about 1-1/2 inches of small, fine stranded copper wire and stick it into the small metal female socket on the Jeep-side connector. With that folded back I had a firm connection to the pigtail with it plugged in. Other guys have had better luck than me sticking a pin in, along side the wire into the connector. Larger wire might bend the socket. (maybe mine did!)

I jacked up the left front frame so the axle was hanging and removed the wheel so it was easy to reach. Freedgr's tip to chop the wires so a 7/8 box would go on the old sensor came in handy.

Topped off the tank, I'll have a "knocken around" mileage number in a few weeks. (XJ.89.Limited).

 

YES! Glad to see you used that upgrade!

 

A little update. At Wall-Mart today I saw they sell a $10 analogue meter. If anybody knows if it works here, feel free to post it!

Was a hash over 3/4 tank as I passed 100 miles, but I had to fill at a different pump, the gauge went a little higher than I remembered it did. More soon....

 

The O2 sensor is like a little battery. When hot it puts out a small voltage - .2-.49 V. Oxygen absorbs or reduces the output voltage. Using ANY analog meter will instantly destroy it. At best they are 20,000 ohms/volt - way too much load.

It HAS TO BE A VERY HIGH IMPEDENCE DIGITAL meter - even then the cheapies are too low.
Use a scanner to see the interpreted voltage from the PCM.

Use a little logic - if it's so sensitive it can sense minor changes of Oxygen content in the air, wouldn't you think it's pretty delicate?

No? Use the wrong meter on it - you'll see!

 

There is more than one type of o2 sensor. And they all operate differently. Which one are you talking about? Heated, universal wide band, or titania...?

 

I add "maybe", "might be", "I guess", "it seems to me", If I posting something I think might be helpful, but am not totally sure.

The Renix 02 sensor is a variable resistor. I believe as the oxygen content in the exhaust goes down, the resistance drops. (or the it's the reverse). The ECU determines the resistance of the sensor by the drop in the 5 Volt feed to it.

Meters are the main point of this thread. Some of us don't have a DRB II, an oscilloscope, or a spendy meter like a Fluke, so I'm seeing what can be done with what's available. Probing the voltage not only apparently did not damage the sensor, but the reading was dead on what would be expected. So far I am very pleased.

Us far as "use a little logic", yea, I don't know if I'd want to hook up up the 9v battery in the meter to the 5 volt feed wire. I do strongly doubt that would ruin it but, at around $70 I wouldn't do it to a working one. (maybe someday with one with a bad heater though)

Side note; Hank, I read the box and what came with the new 02. I was disapointed that NTK didn't see fit to mention weather it was Titania, or Zirconia. I guess I should search it out.

 

Titania based sensors are resistance sensors. These are the NTK ones I hope...

Zerconia, like Bosch, generate small amounts of voltage based on 02 content...but these need a reference...so they have sensors on both sides! Weird eh?

Wide bands have other weird stuff that you could just look up on wiki...like their own little oxygen pumps!

 

Titania



Zirconia



Wide band

 

OK, great! So Titinia for the Renix. Keeping it practical, I want to mention that means installing a new 02 sensor in a renix, you go 3/4 turn past finger tight according to the NTK literature. (is says 1/2 for Zirconia). Thanks!

(so far my research indicates a bonehead just screwing one in seems to work OK though)

 

"""""Probing the voltage not only apparently did not damage the sensor, but the reading was dead on what would be expected. So far I am very pleased."""""

LOL -
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?


Do a little research - the titania sensor was used on Vauxhalls. Renix Jeep only used them occasionally on the early ones - Google.

Bosch does not make them, so every one that can use a Bosch is obviously the voltage type - Google.

Since the CIRCUIT is high impedance, using a low impedance voltmeter will load it down to where the readings you get are not indicative of what's happening anyway.

If you are absolutely sure you have the resistance type go ahead.
But if you are wrong expect to buy a new one.

Best and easiest way - use a scanner that can read it.
Contrary to popular belief - the OBDI systems can be read with a scanner. We did it for years before OBDII. They just didn't store codes.

IF you must read it - use a HIGH IMPEDANCE VOLTMETER - analog meters are not high impedance - they need power to operate the D'Arsenval mechanical meter. A cheapie analog is usually 10,000 Ohms/volt, some are as low as 5,000.
A good analog will be 20,000, where a digital is more like 100,000 - even the cheapies.

Feeling lucky?