MSefi.com read only forum (Jan.15,2018)

I have an ms I processor with a v3 board and standard code. I had the ms working but when wiring the tps on the car I mistakenly connected the vref to the ground wire. now the ms will not work at all. The fuel pump light comes on and then goes out and it does not work at all on the stim. Any suggestions on what I shorted out?

To check for a short in the Megasquirt PCB, power up the Megasquirt on a Stimulator or on the car and check the following points for voltage with a multimeter.

You should find the same voltage as the battery voltage on the following points: S12, S12C, the center legs of Q9 and Q12, the left (non-banded) end of D3, the left leg of U5, and the left (banded) end of D9.

You should have 5 volts at the following points: S5, the two +5V holes in the proto area, the right (non-banded) end of D9, the right leg of U5, the left (banded) end of D19, and pins 1, 20, and 31 of the CPU.

Let me know where you find the correct voltages, and where you find the wrong ones.

Thanks Matt
All the voltages are correct. I have noticed that d 19 has the same resistance in both directions. Could that be the culprit?

If D19 is bad, it will get hot and you'd see zero volts on most of the 5 volt plane.

Matt
I reloaded firmware and now have communication. All gauages are functional on megatune except rpm and pulse width. Where do I go from here?
Thanks my friend

Get the RPM working. How is that input set up?

Matt
I printed the pdf schematic of the v3 board. While checking the circuits at the u3 the ecu came alive and the stim is working. all guages are functional. Is there an issue with the opto isolator?
Thanks for the help so far

You can check the output of the opto-isolator with a 'scope or LED and resistor. The LED should flash like the Stim one. All the opto does is prevent high ignition volts getting to the processor under a fault condition. If you suspect the iso circuit you could try the VR one from the Stim.

got her up and running. started with first crank. now I have to fine tune the computer. Thanks for all your help. I started it with the l jet wiring and a pig tail I built. Now I will hook up the Diy harness all all the assundry sensors. You guys are great!