Megasquirt V3 + 2.21 Stim O2 Sensor Circuit Problems

[lowgman]

Greetings,

I finally finished building my MSII V3 Board and tested it out. I hooked it up to my MegaStim 2.21 and loaded up the latest MS2 firmware.

After that, I started up TunerStudio and was able to get some communications going from the computer to the ECU. All the pots on the stim worked, RPM, CLT, IAT, and TPS. They read normal.

However, when I turn the O2 pot, it doesn't seem to register properly on tuning software. I can turn it, but only the first couple degrees of turns make a few jumpy changes, but in 95% of the pot's range, it is unresponsive. Starting from the most counter-clockwise direction, when I turn the dial (for the first half a turn), it jumps from 14.x AFR to 16.x and then 12.1 all the way through to the end of the pot's range. This is all while the stim is simulating the engine being running.

Here are some troubleshooting steps that I have already tried:

[1] I tested the pot's lead. The outer pins register @ 5 volts, and one of the outer pins to the center pin is variable to the pot. If I turn it fully counter-clockwise, it reads zero, and as I turn it up, it works its way yup to 5 volts.

[2] I put my volt meter on pin 28 of the 40 pin ECU and tested both sides of R10. No readable voltage.

What else can I check? Any ideas on how I can go about troubleshooting this problem?

Thanks in advance!!

[Matt Cramer]

Is your ECU calibrated for a narrow band? If so, it will only change its reading for the 0-1 volt portion and stay stuck when the voltage goes from 1-5 volts.