gooflophaze

Just making this for posterity/googleability in case anyone else runs into it. Don't see any mentions of D13/Q3 letting the smoke out on msextra.

3.57 ms3 w/ ms3x in 94 w/ vvt + turbo. Purchased in 2010. My brother was driving, suddenly IAC was 100% open, little bit of throttle would go into overboost. Clutch in would rev to 4000rpm, tachometer died. Pulled over and I came to help diagnose - pulled the IAC connector, engine was running but didn't sound right, limped it home. Got into it today, verified settings were unchanged, reflashed 1.5.1 firmware and retried, still not running right. Also noticed accessory fan was spinning with key on.

Popped things down on the bench and noticed on jimstim the first row of the MS3x adapter were all lit up. Some more digging into tunerstudio and playing with testmodes, could not turn any of the LEDs off. Removed ribbon cables from the MS3x, and the top row on the MS3x were still powered (Idle, VVT, Tacho, n2o2, boost, n201). Took a closer look at the board, noticed Q3 was a little grungy. Went to the schematic in the hardware and found that it looks like Q3 is acting as a flyback snubber in conjunction with D13. Broke out the hot air and desoldered Q3, threw back on the power, still lit, tested D13 with multimeter and it wasn't diode-ing - failed short - desoldered, and now all the lights were out - except the tacho, which was dimly lit - so it looks like one of the medium current drivers is damaged.

So - just in case your idle is high, your EBC is closed, your fan is on (fan relay driven by one of the nitrous outputs), and your tachometer has gone out, and your VVT is rattling - your MS3x board has died. Gonna look and see if there's a root cause somewhere in the wiring, but nothing recent has been done with it, everything is loomed and taped. More poking in the light of day.