AEM 30-0300 CanBus AFR Gauge
 

Hello!


I have added a AEM 30-0300 AFR gauge and Mega squirt PNP Pro ECU to my Miata. Ive gotten the car to start and idle however I am having some trouble with getting the AFR gauge and ECU to communicate properly using the Can Bus of the ECU.

Before start up and while the AFR gauge is warming up the tuner studio screen shows 26.90 for Exhaust Gas Oxygen 1. After the car starts up and the AFR gauge is warmed up the pod reads 16.5 AFR however tuner studio shows 53.8. Then the reading shown in tuner studio continues to climb and doesn't make sense. After a few minutes it reaches over 200 on the gauge in tuner studio. I have posted a link below to some of my settings but has anyone ever run into a similar problem? I realized that the settings under project properties was set to narrowband - volts but I just changed that to wideband - AFR.


https://photos.app.goo.gl/6hr1ccjYVWfwUGyTA

Your settings look correct in the picture you linked. I would go back and double check your wiring and make sure you have everything connected correctly.

I think I solved the problem and it appears to be an issue with tuner studio. When I first started this project file for my car I had selected narrow band o2 sensor because the wide band wasn't installed at the time. After installing the wide band I switched the project settings to wide band and configured the O2 sensor using the can bus however for some reason tuner studio didn't properly make the changes to go back to wide band. I created a new project and selected wide band from the project setup page and using the same settings the wide band is now reading correctly in tuner studio.

Hey there! I am getting ready to wire up my AEM 30-0310 which is similar to your sensor but without the gauge.

This is my first experience with a standalone and a Wideband.

I'm trying to figure out how to wire up the unit without having tons of cabling hanging out in the engine bay and if it makes sense to route the wires directly to the MegaSquirt.

Looking at the Options Plug it's pretty obvious that I can run the cables to the CANH and CANL connections. But I'm wondering if it's possible to get 12V switched and ground from the MegaSquirt directly. I see a sensor ground (Pin A, which I plan for knock sensor ground) and a 12V (Pin J, but that seems to be limited to 0.5 A and it looks like the Wideband needs 5A).

Should I be tapping power and ground from somewhere else for the sensor? Any recommendations?
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Thanks!

I used a fuse tap to power my wideband from the power window circuit. I found a bolt behind the fuse block that screwed into sheet metal and used that for my ground.

I would recommend that you get one of these fuse taps to add the power for the wide band, preferably from a source that has power during run and start key conditions. Me and silver did the same thing to grab the power for the wide band which will draw close to 3A during warmup of the O2 sensor, too much current for the ECU. Plus I would not want to risk frying my expensive ECU because the O2 wiring melted on the exhaust and shorted the power to ground wires.
https://www.autozone.com/electrical-...-tap/32416_0_0

Really appreciate the help. I'll look at using a fuse tap for the window circuit and ground somewhere that makes sense.

Just curious though, I have a 1995 with the four wire O2 sensor. Has anyone tried getting the 12V from the old O2 sensor harness? Link to FM Four Wire O2 Sensor Whitepaper

That is possible but you would have to investigate where the o2 sensor gets its power for the heater circuit. I took a quick look at my wiring diagram for a 99 and it appears that the o2 heater circuit is from the same switched 12V source as the ignition coils. The only problem would be that this feed is fused at 15A and the AEM calls for a 5A fuse, also I usually avoid cutting into the original wiring of the car because some of us have to go back to stock to pass state inspections :) .

Thanks for the heads up! My plan was to snip the end off of an old O2 sensor and make that into an adapter. Since I agree with you that I typically don't like snipping the vehicle side harness.

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Hi there !
I stumbled upon a similar problem with my AEM 30-0300 as well.
My solution was to go into the AFR Calibration Window, set the sensor to "DIYWB" and adjust the points like this:
Point 1: 0.5 volts -> 8.5 AFR
Point 2: 4.5 volts -> 18.0 AFR
And this works for me... just have to switch the power source cause my MS3 Mini has no clue of the AFR for 7 or 10 seconds till this thing heats up again and gives out any data :yippee:

It looks like the best thing would be to connect the WBO2 to an IG1 power source, which is on during both ON and START. I have mine connected to the power windows (IG2) and have the same issue where starting turns off the WBO2 and I have to wait for it to boot up before getting a reasonable signal.

https://cimg7.ibsrv.net/gimg/www.mia...3952b546aa.jpg

I can't figure out where this is supposed to be or which plug this is... Can you tell me ? ^^

This is the ignition switch, and IG1 is one of the output pins.
Not sure where the best place to tap into it would be.

https://cimg8.ibsrv.net/gimg/www.mia...dc31652d4a.png

I have an idea... Before i installed my gauge under the radio there was a compartment with a watch. As far as i know the watch was allways powered. So i'll try it there and let you know (with pictures maybe)

You may drain the battery this way. The heater on the WBO2 will be constantly running.

Oh... Yeah brainfart was about to happen...