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Hi all, I apologize for the newbie questions. I don't know much about cars, which is why I got the Miata and started tinkering. I've definitely bitten off more than I can chew so I'd greatly appreciate any guidance.
I've installed an MS3Pro-PNP ECU into my Miata. I took out the narrowband O2 sensor and installed a wideband O2 sensor (AEM X-series). I'm currently stuck. One issue I have is that I cannot detach the MS anymore. The upper nut is very hard to reach and keeps spinning even with a ratchet on it (can't reach the other side). I was hoping to detach the cables and cut/solder them in the car. Regardless of what I have to do I'll probably have to pull the cables out of the MS and try to make the appropriate connections. I wanted to run my plans by you guys before committing. I've included the O2 sensor and MS3PNP wiring/connector data below.
1. I've read so many conflicting things about where to put the wideband O2 sensor. It's definitely less than the 45 cm away from the exhaust manifold recommended by AEM. Is that accurate? I've already installed it so I'm OK to leave it for now, as long as it won't cause major issues. My understanding is that placing it where the narrowband O2 sensor used to go will work, but may limit the lifespan of the O2 sensor. Is that accurate?
2. Where do you feed the wideband sensor cable through the firewall? I wanted to use a grommet that most people seem to have in their videos, but I cannot see where it comes out the other end inside the driver's side of the cabin. If I shine a light through I can see it but it's stuck behind a barrier. I currently have it going through the same place that Megasquirt recommends the MAP vacuum line goes through. Is that OK?
3. What would you recommend for optimal power source / ground wiring? I was initially going to splice the power source / ground for the sensor to the yellow and black cables of the cigarette lighter, but I was reading that the ground should be near the ECU to avoid voltage offset. The MS manual says "You should ground the wideband to the engine block near the factory ECU ground wire to ensure an accurate reading." Braineck recommended using the ECU itself. Can I do the following:
Cut the red cable (35) of the White connector pinout, connect a 5A fuse to it, and then connect a red cable (+12V) from the O2 sensor to it with solder and butt connectors
Cut any of the black cables on the Gray connector pinout (3, 5, 7, 9, 18) and connect the black (ground) cable from the O2 sensor to it with solder and butt connectors
Would that work? Is there an easier way?
4. What would you recommend for connecting the O2 analog output (0-5V) cable to the ECU? Do I have to connect the sensor ground? An earlier Braineck post suggested that I didn't have to, but I'm not sure if this is for the same version of wideband O2 sensor.
The manual states "You can either connect the analog output to an available analog or EGO input on the option connector, or you can cut and splice the oxygen sensor signal wire to the analog output. Note that not all models have a specific EGO input pin on the options connector; models that do not have an EGO pin will normally have one or more analog input channels on the options port. If you use the EGO input pin on the options connector for wideband input, you must disconnect the stock oxygen sensor. Do not ground the oxygen sensor wire if you disconnect it; leave it completely unconnected and taped off if necessary (make sure it can't short to ground or anything else)."
The extended manual says "The three general purpose analog inputs may also be configured as additional O2 input channels and work in the same way when set up as O2 inputs." This seems like it would be easier.
Can I cut the light blue cables going into Pin 19 (or 20, 21) of the White Connector Pinout and then solder on the white analog 0-5V input from the wideband O2 sensor? If I do that, can I just switch the input in TunerStudio to be from there instead of the stock O2 sensor?
Is this a reasonable plan? Is there an easier way? If I was going to be cutting cables anyways, should I just cut the pink cable (25) of the O2 input?
Why are you going to use the analog input for the wideband controller with the potential grounding voltage offset/accuracy problems?
You already have the AEM X-series and MS3pro, this combo can work via CAN Bus.
What he said. If you aren't using any other CAN devices, it's super simple to user the CAN input on the ECU. Just wire your CAN +/- into the ECU and select CAN for your EGO. I've got MS3 Pro with the 30-0300. then no need to worry about offset grounds. Also running power from the ECU as recommended by Brain.
How would I go about getting power from the ECU? Can I do the following?
Cut the red cable (35) of the White connector pinout, connect a 5A fuse to it, and then connect a red cable (+12V) from the O2 sensor to it with solder and butt connectorsCut any of the black cables on the Gray connector pinout (3, 5, 7, 9, 18) and connect the black (ground) cable from the O2 sensor to it with solder and butt connectors
I managed to get it up and running. I used the window power (DIYAutoTune strongly recommended not using the ECU power) and the CAN port as suggested earlier.
I also used the window power supply for my WBO2 install. I have manual windows so it was easy to repurpose with the right fuse for the WBO2. I de-pinned the connector and ran it through the grommet behind the handbrake.
I have a gauge on the MS CANbus, so I had to use the analog output on the AEM X WBO2.
I verified the analog output value vs the digital serial (not CAN) output as matching within 0.1 AFR.
09-28-2020 | 04:54 AM
Wideband O2 Connection
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