Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
O2 Voltage readings - which wire???
Author Message
tat3r Offline
Member
***

Posts: 19
Joined: Jun 2009
Reputation: 0
Post: #1
O2 Voltage readings - which wire???

I have a 95 Jaguar XJ6 with two O2 sensors utilizing 4 wires.
I have checked the voltages of all 4 wires before the wiring harness connector. I have found the heater wire using approx 14V's.
I recently acquired a complete wiring diagram from the local Jaguar dealership (over 100 pages) and appears that I've located the output wire that I need to splice my EFIE connectors to:
refers to the wires on the backside of the wiring harness - 1 GREEN and 1 BROWN.

My issue is that when I take voltage readings on these wires I'm not getting the .2 to .9V (200 - 900 mV?) everyone is talking about. I'm getting a reading that fluctuates every 1.5 seconds between .12 to 4.75 Volts?!?! Fluctuates up and down between those two approx ranges, doesn't seem to steady out (at least after the car has been running and I measure for approx 20 sec's)

Is this indeed the wire I'm looking for?
If so, how is my EFIE going to have any effect if I'm just pushing out 200 - 350 mV?

Here are my voltmeter measurements before the harness on all 4 wires.
-- yellow wire - @ .021 to .029 (meter set on 2000m)
-- black wire - @ .12 - 4.74V
-- red wire - @ 14.07 - 14.17
-- white wire - @ 0

There are only 3 wires on the backside of the wiring harness. I am supposing that the White and Yellow are possibly Ground wires and their connection is combined and the other is power to the heater and the remaining is the output to the ECU - which appears to be the BROWN wire on one harness and the GREEN wire on the other O2 harness. But what's up with the wild Voltage readings??? How does my EFIE deal with that?


Can anyone help on this?

Additionally, there doesn't appear to be a MAP, but there is a MAF, I assume my MAP/MAF sensor enhancer (the potentiometer) connects to the output of this wire? (at idle was reading 1365 mV - revving engine reading 1900+ mV - meter set on 2000m)

Thanks
06-15-2009 06:34 PM
Find all posts by this user Quote this message in a reply
colchiro Offline
Moderator
*****

Posts: 3,265
Joined: Feb 2008
Reputation: 11
Post: #2
RE: O2 Voltage readings - which wire???
Hi Tat3r. Sounds like you have the right wires except for the goofy one.

Have you traced them to the sensors to confirm you have the right ones? (I'm not sure what you meant by "backside".)

That black wire should also be a ground. 1995 should be narrow band and every US vehicle I'm aware of in those years had narrow band, with 0-1 volts dc.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
06-15-2009 07:27 PM
Find all posts by this user Quote this message in a reply
tat3r Offline
Member
***

Posts: 19
Joined: Jun 2009
Reputation: 0
Post: #3
RE: O2 Voltage readings - which wire???
(06-15-2009 07:27 PM)colchiro Wrote:  Hi Tat3r. Sounds like you have the right wires except for the goofy one.

Have you traced them to the sensors to confirm you have the right ones? (I'm not sure what you meant by "backside".)

That black wire should also be a ground. 1995 should be narrow band and every US vehicle I'm aware of in those years had narrow band, with 0-1 volts dc.

Hey Colchiro, thanks for your response.
By "backside" I meant the otherside of the wiring harness that the O2 sensor wires plug into.

The O2 sensors are quite accessible and easy to trace. The 4 wires connect at a harness that has 3 wires that come out the other side ("backside"). My wiring diagram shows that the output wires going to the ECU, from the backside of the wiring harness, should be the GREEN wire on one and the BROWN wire on the other.

I have measured the voltages on these wires numerous times on probably 3 different days (I'm sure I'll do it again, too) and I still get the .12 to 4.75 fluctuation.
06-15-2009 07:34 PM
Find all posts by this user Quote this message in a reply
colchiro Offline
Moderator
*****

Posts: 3,265
Joined: Feb 2008
Reputation: 11
Post: #4
RE: O2 Voltage readings - which wire???
The o2 side is easiest to trace when you can follow the sensor right up to the harness. Kind of hard to get that wrong.

I asked Mike for his opinion.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
06-16-2009 03:21 AM
Find all posts by this user Quote this message in a reply
mike Offline
Senior Member
****

Posts: 2,023
Joined: Jul 2007
Reputation: 7
Post: #5
RE: O2 Voltage readings - which wire???
You have a titanium dioxide oxygen sensor and its range is not the standard oxygen sensor range. It operates using larger voltages. It also uses both upstream and downstream sensors and compares the two voltages to do it's air/fuel calcs. It uses 1.1 for rich and 3.3 for lean. Therefore, aside from being a different voltage range, the logic of rich and lean are reversed. In other words, other oxygen sensors use the higher voltage to show rich, and lower voltage to show lean.

I hope you have a Dual EFIE Deluxe from FuelSaver-MPG. If so, you can rather easily solve this. First you'll need to change the range of the EFIEs. We have a document on the http://www.fuelsaver-mpg.com/documents.html page that will show you how to do it. See http://www.fuelsaver-mpg.com/doc/RangeAdjust.html for instructions. Follow the directions exactly. Increase the range to about 1.5 or 2 volts. This will allow you to adjust the voltage of the signal by larger amounts, instead of only .5 volts. Only the Dual EFIEs have the range adjustment pots that allow you to do this.

Then, when you install the EFIE, reverse the computer and sensor wires. Put the white (and blue) wire to the sensor and the green (and brown) wire to the computer. This will have the effect of subtracting voltage from the signal instead of adding voltage.

I don't really know how much voltage you can set the EFIE to on this application. I would start out at about .5 volts, and see what happens. My guess is you'll end up with higher voltage, closer to 1 volt, when you get it tuned. Use the same voltage at both front and rear sensors.

This of course is somewhat experimental, and you should understand that. But I think by following these directions you should be able to get the result you want.

[Image: signature.gif]
Visit Our Documents Page
06-16-2009 08:44 AM
Visit this user's website Find all posts by this user Quote this message in a reply
colchiro Offline
Moderator
*****

Posts: 3,265
Joined: Feb 2008
Reputation: 11
Post: #6
RE: O2 Voltage readings - which wire???
Thanks Mike.

Tat3r, please update this post with your findings so we have a record of the resolution.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
06-16-2009 12:48 PM
Find all posts by this user Quote this message in a reply
tat3r Offline
Member
***

Posts: 19
Joined: Jun 2009
Reputation: 0
Post: #7
RE: O2 Voltage readings - which wire???
(06-16-2009 08:44 AM)mike Wrote:  You have a titanium dioxide oxygen sensor and its range is not the standard oxygen sensor range. It operates using larger voltages. It also uses both upstream and downstream sensors and compares the two voltages to do it's air/fuel calcs. It uses 1.1 for rich and 3.3 for lean. Therefore, aside from being a different voltage range, the logic of rich and lean are reversed. In other words, other oxygen sensors use the higher voltage to show rich, and lower voltage to show lean.

I hope you have a Dual EFIE Deluxe from FuelSaver-MPG. If so, you can rather easily solve this. First you'll need to change the range of the EFIEs. We have a document on the http://www.fuelsaver-mpg.com/documents.html page that will show you how to do it. See http://www.fuelsaver-mpg.com/doc/RangeAdjust.html for instructions. Follow the directions exactly. Increase the range to about 1.5 or 2 volts. This will allow you to adjust the voltage of the signal by larger amounts, instead of only .5 volts. Only the Dual EFIEs have the range adjustment pots that allow you to do this.

Then, when you install the EFIE, reverse the computer and sensor wires. Put the white (and blue) wire to the sensor and the green (and brown) wire to the computer. This will have the effect of subtracting voltage from the signal instead of adding voltage.

I don't really know how much voltage you can set the EFIE to on this application. I would start out at about .5 volts, and see what happens. My guess is you'll end up with higher voltage, closer to 1 volt, when you get it tuned. Use the same voltage at both front and rear sensors.

This of course is somewhat experimental, and you should understand that. But I think by following these directions you should be able to get the result you want.

Thanks for the detailed input. I'm going to have re-read this several times to really comprehend it. As you all can tell, I'm not very savvy electrically-speaking.

I wanted to mention a couple things regarding your input to make sure you knew:

Not sure if you were getting your info from ALLDATA.COM, b/c I had a buddy pull it up, but the schematic on the O2 sensor only shows 2 wires, but my O2 sensors have 4 wires. Perhaps in the schematic they are only showing the input and output wires and ignoring the grounds or heater wires. You would know better than me on that.

Additionally, if the fluctuation is supposed to be 1.1v to 3.3v, then why am I getting readings of .12V to 4.75V (changes approx once every second) on my voltmeter?

Additionally, if the ECU uses measurements from the O2 sensors both pre and post Cat, then how will the adjustments you mention making not be corrected by the post-Cat O2 sensors?

I'm not debating your assessment, I'm just trying to better understand.

Thanks
(06-16-2009 08:44 AM)mike Wrote:  You have a titanium dioxide oxygen sensor and its range is not the standard oxygen sensor range. It operates using larger voltages. It also uses both upstream and downstream sensors and compares the two voltages to do it's air/fuel calcs. It uses 1.1 for rich and 3.3 for lean. Therefore, aside from being a different voltage range, the logic of rich and lean are reversed. In other words, other oxygen sensors use the higher voltage to show rich, and lower voltage to show lean.

I hope you have a Dual EFIE Deluxe from FuelSaver-MPG. If so, you can rather easily solve this. First you'll need to change the range of the EFIEs. We have a document on the http://www.fuelsaver-mpg.com/documents.html page that will show you how to do it. See http://www.fuelsaver-mpg.com/doc/RangeAdjust.html for instructions. Follow the directions exactly. Increase the range to about 1.5 or 2 volts. This will allow you to adjust the voltage of the signal by larger amounts, instead of only .5 volts. Only the Dual EFIEs have the range adjustment pots that allow you to do this.

Then, when you install the EFIE, reverse the computer and sensor wires. Put the white (and blue) wire to the sensor and the green (and brown) wire to the computer. This will have the effect of subtracting voltage from the signal instead of adding voltage.

I don't really know how much voltage you can set the EFIE to on this application. I would start out at about .5 volts, and see what happens. My guess is you'll end up with higher voltage, closer to 1 volt, when you get it tuned. Use the same voltage at both front and rear sensors.

This of course is somewhat experimental, and you should understand that. But I think by following these directions you should be able to get the result you want.

After reading through your explanation again, I have an additional question:
Are you talking about connecting an EFIE to both Pre AND Post cat O2 sensors? I have 2 O2 sensors pre and 2 post - for a total of 4 (I realize my math is astounding, I know! Ha ha).

If that is what you are talking about - is there an EFIE than can do that?
(This post was last modified: 06-16-2009 09:01 PM by tat3r.)
06-16-2009 08:02 PM
Find all posts by this user Quote this message in a reply
colchiro Offline
Moderator
*****

Posts: 3,265
Joined: Feb 2008
Reputation: 11
Post: #8
RE: O2 Voltage readings - which wire???
The additional two wires are for the heater on your o2's (+12v and ground).

You'd need a second efie to treat the post cat o2's.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
06-17-2009 03:36 AM
Find all posts by this user Quote this message in a reply
mike Offline
Senior Member
****

Posts: 2,023
Joined: Jul 2007
Reputation: 7
Post: #9
RE: O2 Voltage readings - which wire???
That sensor definitely has a heater and a ground. It is a regulated heater in that it is not on all the time. The sensor must maintain a temperature in a fixed range for that type of sensor to work properly.

And yes, I did get all of the information from Alldata.

The range of the sensor is NOT 1.1 to 3.3. What the sheet said is that below 1.1 is rich and above 3.3 is lean. I think they are implying that between 1.1 and 3.3 is undefined. But the voltages you gave seem consistent with this information.

[Image: signature.gif]
Visit Our Documents Page
06-17-2009 08:51 AM
Visit this user's website Find all posts by this user Quote this message in a reply
tat3r Offline
Member
***

Posts: 19
Joined: Jun 2009
Reputation: 0
Post: #10
RE: O2 Voltage readings - which wire???
(06-17-2009 03:36 AM)colchiro Wrote:  The additional two wires are for the heater on your o2's (+12v and ground).

You'd need a second efie to treat the post cat o2's.

Dammit! ha ha, So I'm going to need 2 EFIE's??? This is just getting more and more expensive - I'm sure I'm approaching or at the $500 mark on equpment and supplies.

So, based on the ALLDATA am I to assume that the voltages would be the same?

Additionally, I noticed in some postings that the post-Cat O2's are analog - how am I to know if mine are analog or digital? AND what kind of EFIE to get?
06-17-2009 10:24 AM
Find all posts by this user Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 1 Guest(s)