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Problems setting up wideband on powersports ECU


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Complete newbie, forgive me. I have a Vi-PEC motorsport ECU for my 2013 Polaris RZR XP 900. I plan on getting the vehicle professionally tuned in the near future, but in the meantime I think I should be able to get it nominally running. Before I can do a QuickTune I need my AFR reading working properly. I have an AEM AFR gauge. It supports "0-5V" data logging. Specifically, AEM says it supports linear logging with the following data points:

min = 8.5:1 AFR = 0.5V

max = 18:1 AFR = 4.5V

In terms of wiring, from the AFR gauge:

*WHITE - Connect to Lambda + Input.

*BROWN - Connect to Lambda – input. (Must be connected if Lambda + is used)

I have the WHITE wire hooked up to Expansion Connector pin #10 (AN Volt 5).

I have the BROWN wire hookup up to Expansion Connector pin #12 (Sensor GND).

I have setup "Analog Input" "AN Volt 5" as type "Lambda 1" and have set calibration to "Cal 4".

I have setup "Cal 4" thusly:

Input Value A: 0.50 V

Input Value B: 4.50 V

Output Units: Lambda

Output Value A: 0.580 Lambda

Output Value B: 1.220 Lambda

I have also tried entering AFR equivalent values for "Output Value A" and "Output Value B".

Regardless of what I set the Cal 4 Output Values to, iVTS always shows the value as the highest value there is (equivalent to the 4.5 V setting). If I give it a little gas, the value actually drops a little bit.

Googling the issue, I found something at http://www.learntotune.com/discussions/ ... -your-ecu/. According to that thread, AEM EUGOs are notorious. One post in that thread recommended the following:

AFR : 9.77 Volt : 0.00

AFR : 19.90 Volt : 5:00

I tried those settings, too, but the AFR stayed mostly at 19.9:1--again, basically the max value.

At this point I disconnected the wires from the AEM AFR gauge and measured the voltage with a multipmeter with the motor idling. It read about 2.3 V. The gauge itself read 12.5 for so. The two values seem correct. What doesn't seem correct is the value the ECU is reading.

I tried hooking up the BROWN gauge wire to a chassis ground instead. It didn't help.

Can anybody suggest a course of action for me?

Thanks in advance,


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Hi Sean

First step will be to check the voltage the ECU is seeing on Volt 5.

Easiest way to do this would be to set the input up as a GP voltage 0-5.

This way you can read the raw voltage and check it is a match for the expected output of the unit.

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Hi Simon,

Thanks for your reply. With your advice I was able to get it working. I had made two fundamental errors.

First, I had the wires pinned incorrectly. I had a custom aux harness made with a Deutsch connector at the other end of the cable. I didn't realize that one end had pinouts like this:

1 2 3 4 5 6

7 8 9 10 11 12

whereas the other had:

1 2 3 4 5 6

12 11 10 9 8 7

Once I corrected that I was able to see fluctuation in the voltage so I knew I was getting closer. But the AFR shown in QuickTune was still not even close to what the AFR gauge was displaying so I knew I had some work left to do. The second part of my problem was that I was using AFR values instead of Lambda values for the Cal4 setup. I had used AFR values because I had chosen "Imperial" instead of "Metric" in the units setup section. And for Imperial measurements I have AFR selected, whereas for Metric, Lambda is selected. Being in the US, I use and work with Imperial units, Therefore I would have thought that I should enter the "A" and "B" values asked for in the Cal4 setup in AFR units (e.g, 8.5 for low and 18 for high). That would not be correct however. Once I adjusted the input units to Lambda values (0.58 for low and 1.22 for high), the measured AFR now matches with the gauge's reading perfectly.

I was even able to QuickTune a few cells.

Thank you so much for your suggestion!



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