I have a question about MS3 board (Daughter card) repair. I have an MS3 with a V3.0 main board and the MS3X expansion that I purchased in February. It went together well and I got the car up and running fairly easily. I was very impressed with the products. However, about a week ago I ran into a problem. I had driven the car to work and it ran perfectly. When I started the car after work, it idled pretty rough so I connected my laptop to to use tuner studio to see what was happening. I saw that there was some sync loss and some of the sensor reference voltages were incorrect (no data log). I immediately started to look through my wiring harness for any shorts or problems. I found none and I had to get the car home so I drove about one mile and decided that I needed to pull off of the road and make a better inspection of the wiring. I turned the car off and inspected the wires again (both visually and with a digital volt meter). I did not find any problem with the wiring harness so got back in the car and tried to take another look in tuner studio but the MS3 would no longer communicate with tuner studio or power on. When I installed the MS3, I left my factory wiring and ECM in the car for just such an event, so I was able to switch back over to the factory ECM and drive home with the MS3 disconnected.
Since then I have inspected the V3.0 main board, the MS3 daughter board and the MS3X board. I found that polyfuse 1 F1 was tripping and that the 5 volt regulator was damaged, so I replaced both but the polyfuse continued to trip. upon inspection of the MS3 Daughter board I found that the VCC circuit on the MS3 daughter board has a short somewhere. There is only 1.2 ohms resistance at any point between Vcc and ground on the MS3 daughter card with the daughter card removed from the main board. And with the daughter card removed from the main board, the main board ohms correctly everywhere. However, if i return the daughter board to the main board, all vcc points on the daughter card and the main board have only 1.2 ohms resistance between Vcc and ground. And if 5 volts is applied directly to the vcc pin on the 40 pin connector for even a second (whether in or removed from the main board), the processor starts to heat. I am worried that the processor itself has the short. I inspected all pins of the processor using a 100x-300x microscope to see if there was any solder bridge or similar short but I was unable to find any problem and no components are visually damaged. I am certain that the short is on the MS3 daughter board but without a correct schematic for the board it is more than difficult to make an accurate diagnosis of the specific component that has shorted to ground. I do have experience soldering and testing SMD components but I would still be limited to testing only the capacitors, resistors, and diodes.
My setup at the time of the problem was MS3 with MS3X card and v3.0 main board running Beta 19 firmware. Full sequential fuel on a V8. Fuel only at the time of the problem however it was set up for COP with GM optispark being used for crank/cam signal. I am not using the IAC output but the main board is wired for a 4 wire IAC. I have been running the car on the MS3 for about 2 months and I had not made any hardware changes in more than 6 weeks before the problem. Sorry this was a long post. I have contacted DIYAutoTune.com and let them know. I am waiting to hear back from them. What I am looking for here is possible causes, any ideas on the specific component of the MS3 daughter board that might be the culprit, and hopefully any help I get can help others. There is no MSQ and datalog because I am fairly certain that they won't do much to help. Thanks