MSPNP Pro abruptly goes Off Line while driving

[poormxdad]

My MSPNP Pro dropped Off Line well over a dozen times while driving my 1999 Miata, trying to get her home from the track yesterday. I had two drop offs on track. She ended up on a flat bed. I've attached a log that shows suddenly the Alternator Target Voltage goes to 0. I don't know if it is a symptom or the cause. I've attached one log, but I have others that are pretty much the same.

At 397.066s Alternator Target Voltage goes to 0. One more click of the Right Arrow key and the time jumps to 506.090s. I assume the missing interval is coasting to a stop with the key on, engine off, PNP Pro Off Line. Then it takes another second or so for the log to show the minimum Battery Voltage, in this case 9.8V. Alternator Target Voltage doesn't start to go up till 508.978s. I assume I am attempting to start the car and the MS is on line. What would cause TS or the PNP Pro to make the Alternator Target Voltage 0? Or, is the MS going offline and that Alternator Target Voltage of 0 is just one of the last things recorded?

Since I actually had the laptop hooked up, I did notice a few other things. After she would die, sometimes I would turn the key to restart and nothing. TS indicated Off Line. Sometimes after she died, I would turn the key on and I would only hear part of the normal fuel pump prime cycle. Maybe half. It would stop, and TS indicated Off Line. But if I turned the key, got the full prime cycle, and TS indicated Connected, she started normally every time. I've also attached a Composite Log I took when trying to restart the car. I do not know if it captured anything.

This is a new problem. Otherwise, the car is a beast. The Off Line issue happened in shorter intervals each time on the way home. It got to the point where I needed to call for a tow. I've since checked all the grounds, including the one on the powerplant frame. I made sure the connectors were seated in the PNP pro. I replaced the camshaft position sensor and pigtail. I replaced the battery. I'm out of ideas.

Help!

[Matt Cramer]

The target voltage drops to zero when the engine stalls and the alternator control remains offline until a short time after a successful start. That part is normal behavior.

Does the going offline only happen with the engine running, or can it happen key on and engine off? Are you able to measure the VREF voltage when it drops offline?

[poormxdad]

Matt,

Just FYI, I replaced the main relay this afternoon and drove around my town. She cut out after about 6.5 miles. CLT was about 200 and MAT about 110. It was hot and humid.

I have only had it happen while I was driving.

Not sure what VREF is, but I have not measured it. I did not have the appropriate meter with me when the cut outs happened. What would I need to do? I still need to track this down, so I assume more driving or idling in the driveway is in store.

Thanks,

[poormxdad]

Matt,

In the log I provided in Post #1, the ECU Temp shows 235 or so right before it drops Off Line, then 245 after she starts back up. Is that a real number, and is that normal?

Thanks,

[Matt Cramer]

Probably not a real number - check what it is when you turn the key on with a cold start. If it's off, check which calibration your tune is set for.

[poormxdad]

Okay, so it's not the battery. Not the main relay Not the camshaft position sensor. The Alternator Target Voltage dropping to 0 is normal. The ECU Temp numbers are probably not real.

What do I investigate next?

Thanks,

poormxdad

[Matt Cramer]

VREF is going to be at pin H on the 26 pin options port on the back.



See if you can hook a volt meter to it with alligator clips and see what happens to the voltage when the board goes offline.

[poormxdad]

So stick one of the wires that came with the kit into port H, alligator clip the red side of the meter to it, and the black side to ground?

Thanks,

[Matt Cramer]

Yes. I've responded to your PM about an RMA, but if you can do this test before sending it in, this will help us narrow down what to test it for.

[poormxdad]

I will certainly try. Is it an instantaneous reading, meaning I have to be watching the instant it happens?

Thanks,

[Matt Cramer]

It's probably going to read the same thing the whole time the unit is offline.

[poormxdad]

I'm finally getting a chance to check the voltage as you directed.

With the car started and running, the voltage from Port H was rock steady at 4.95V. It was a much cooler day, about 83 degrees ambient. She ran for 32 minutes, then died. The voltage was 1.648. I recycled the key and got the full fuel pump prime cycle and she restarted. The multimeter read 4.96V and was rock steady till she died again 25 minutes later. I saw the voltage fluctuating and settle out at 1.708V.

What next?

Thanks,

poormxdad

[Matt Cramer]

Email me at support@diyautotune.com and I'll get you a return form to send it in for warranty repair. We'll get this taken care of.