Megastim IDL does not light up

[r3dplanet]

Hi there.

My brain has successfully turned to pudding following my first-time MS project. I have built up an MS2-v3.0 board and flashed it with v3.2.4 firmware, along with instructions for modifications for IAC stepper valve and inputs from an MSD-6AL unit.

I'm finally at the point where TunerStudio shows the correct gauges and each of the five pots on the Megastim 2.21 board control each function more or less correctly. I'm pleased to have achieved this result.

Here is my question: On the Megastim board, the IDL light never illuminates which it is supposed to do depending on where the coolant temperature pot is set. I'm not exactly sure what to do at this point. Perhaps I've failed to burn some setting to the MS board? Maybe I didn't solder something correctly?

I find the TunerStudio software quite confusing, seemingly with options everywhere and nowhere at the same time. At this moment under Startup/Idle -> Idle Control -> I have the algorithm set to On/Off valve.

Thanks for any help.

-marcus

[Matt Cramer]

The settings look OK. Does the CPU try to send 5 volts through R19 when the temperature reading is below 140?

[r3dplanet]

Yes. Below 140 I get 5v at R19. Above that it turns off.

[Matt Cramer]

Check Q4 and Q20 for any solder bridges.

[r3dplanet]

You're some kind of wizard. Q4 and Q20 are not installed because I had originally decided to use a PWM idle valve. A month later, I decided against it and removed the circuit and instead modified the board for an IAC circuit. Reading the PWM section again, I see that I need to install Q4 and Q20. Ack. It's clearly a case of looking at the same thing for too long and not seeing what's in front of me. I'll pop in a couple of transistors and see what happens.

Thanks!

[r3dplanet]

Okay. I popped in almost the correct transistors and now the IDL light works perfectly. I went around to every electronics shop in town but nobody had a ZTX450 transistor, so I substituted a 2N2222 temporarily. As far as I can see, the ZTX450 can handle a load up to 2000ma whereas the 2n2222 can only handle 600ma. I don't want to risk anything, so I'll be sure to swap them out before I drop this into my car.

Now I just need to understand why the I2 LED doesn't light, but that's a story for another time.

Thanks for everything!

-marcus