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Need voltage output from 02 sensors.

3901 Views 11 Replies 3 Participants Last post by  87frankenstang
Wideband O2 to AFR controller to ECU

Hey guys.

I installed my MXT-L AFR controller along with a bosch style wide band in my driver side bank. I need to know the voltage output from my o2 sensor that my ECU needs to read lamda (or shall I say lean/rich) as I can define this in my controller.

I found this: Oxygen sensors | Mustang Forums at StangNet . It stated that at lean it will read less than 400 milivolts and at rich it will read over 600 milivolts with an overall range of .1 to .9 volts. So I did the math and this is what I got:

.1 to .4 volts is lean
.5 volts is lamba
.6 to .9 volts is rich

I included a screen shot of the factory defined analog output voltages for the MXT-L. By FACTORY DEFAULT it's allocating 1 volt as lamda, .5 volt at full lean and 1.5 volts at full rich. I will change this to the aforementioned calculations. Do my calculations look and seem right? Can anyone confirm this information? I just want to make sure I have the right info and only need to program my controller once...


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So I hooked up the analog one output on my MXT-L controller to pin #43 (Dark blue with green) on the connector to the ECU. I defined my controller to read out lambda, and .1 volts at .5 lambda and .9 volts at 1.5 lambda. During the first start she died, but the wideband was still heating so it did not give a reading. I let it heat then she fired right up. No oscillations in the rpms. I took the mustang for a spin and it appeared that she was giving accurate readings but I was mostly around the 16 mark. I logged it and attached the logged to this thread.

I did have one hiccup that was good and bad. Bad: The MXT-L froze at 22.4 while I was cruising in 3rd around 2100 rpm. The motor stuttered for about 15 seconds while it froze. I tried to put it under load to enrich the AFR and nothing... still stayed at 22.4 and bogged the motor. The meter then slowly went rich back to 16 and she ran puurrrfect Laid the hammer and she responded. The GOOD: The output from the MXT-L to pin 43 did have an affect on the motor; it's the right connection and the voltage outputs are right.


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Thanks for posting this, I am going to dealing with this exact issue putting my 306 back in my car (engines finally back from the builder).

I have the same wideband guage, originally I was going to install a new bung and run the wideband seperately and have the ECU read off the narrowbands like factory. Then I read the manual on the wideband and found out it does provide this narrow band output.

Is your check engine light on? I was concerned of the computer throwing a code becuase it didnt see the heater anymore for the factory o2 sensor.

Also, if im not mistaken Analog out #2 is pre-set from factory for a simulated narrow band output. What you posted in that screenshot shows analog out #1, from 0-5 volts which would be what you would use to feed an ECU that is looking for a wideband input. Basically its the defualt output you would if you were doing exactly what we are doing with a car that came factory with a wideband sensor.
Awesome! I posted this thread to help someone who was as clueless as I was haha. My check engine light is not on from the wideband. With the MXT-L you can define what you want the output to read in (lambda or AFR) and you have the ability to define the voltage output for the said reading. The picture I posted was of the default screen, I have since changed it to .1v for .5 lambda and .9v for 1.5 lambda which puts the x and y axises at .5v for stoich. I saw that the analog #2 was already defined for lamda, but since I needed to change it anyways, I just went ahead and made #1 what I wanted. I'll try to get another screen shot of it.
Is your check engine light on?
Correction to my previous statement, my check engine light IS on.
Okay, do you know if that's because you are using the wideband to feed a signal into the ECM and its not "seeing" the original o2 sensor?

Or is it on for some other reason?

Just curious. I mean, I don't really care all that much. Im pretty sure my CEL will be on for a while anyways until I get a quarter horse tuner, since I am not putting any of my emissions stuff back in. EGR, Evap, Smog Pump, etc.
I do not believe the CEL is on due to the MTX-L as that it is only replicating the output voltage of the OE narrowband. I'm still having issues with it freezing on me. :-/
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