JimStim Wiring Cheat Sheet

Through a bunch of research on this site and others, I was able to figure out the issues I was having on getting results to show up when bench testing some ECMs I pulled from the scrap yard. I did two 16197427s and one 1227747. Thought I would share my wiring schemes in case anyone needs these later on.

One thing I can say after testing the 160 and 8192 baud units is what a difference the faster speed makes! I thought I was having communication issues with the '7747 but turned out I was just turning the knobs to quickly on the sensors.

My test bench needs a lot of cleaning up but worked great for some weekend fiddling. Now that I've proven out the PCMs, I've started the TBI rebuild. I wired a vehicle for a Megasquirt application, so wiring the Corvette shouldn't be too bad.

Hope this info helps!

It looks like we were doing the exact same thing on the exact same weekend. :)
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You have a much more organized layout with the barrel connectors. I just stripped wire and tightened them down I the terminals. It crossed my mind that I could make an adapter with a DB37 connector for an easier setup each time, but sold ring to those cups is not a favorite past time for me.

To talk to the ALDL connector, I ended up using an old interface I'd made a decade ago based around a MAX233 chip. Worked great, tuned it up this past week with a real OBD1 connector (I used cut pieces of paper clips before and inserted them into the A and M terminals), then a new serial cable wire running to a USB adapter. Went this route after my attempts to mate the OBD1 cable to an FTDI/USB TTL cable failed in multiple ways.

My wires are just stripped and tightened too. I initially started using a DB37, but it was getting so crowded, so quickly...and I knew it be far easier to troubleshoot (and probe) if I could spread things out. Then I went a bit crazy with the label maker...
I just grabbed an actual ALDL connector out of the salvage yard yesterday...I'd just been using alligator jumper leads.

I think I might throw together a little proto-board with some led's, pull-up/down switches, and maybe a few simple 555 pwm generators...just to break out all the outputs and stimulate the remaining inputs. I also received some digital potentiometers in the mail the other day, so I may try to wire up an Arduino to drive those, to control TPS, MAP, Coolant, etc...I thought then a script could be written to hit every single point in a table (rather than trying to move multiple knobs by hand). That may be (definitely is) a bit beyond necessary, but might be kinda fun/interesting.

If I get really ambitious, I may try making a board that rolls it all together...more to force myself to practice PCB layout, than out of actual necessity. I like the JimStim, but do wish it had a few more I/O, and was a bit less crowded and more clearly labeled...I know it is designed for Megasquirt, but it's about 95% of the way to being a universal ECM stimulator.

What are you using to communicate between the ECM and your computer? Years ago I built a box using a MAX233 chip to link between the 8192 baud feed on a 6.5L diesel. Are you using an Arduino? I've dabbled with those and think they could be about the coolest little gizmos ever, if only I could come up with a practical use! I used an Uno last week in attempts to simulate a speed sensor to bench test a cruise control module. Pretty sure the Arduino part was fine and the module was toast, but don't have a second u it to confirm.

What inputs are you missing on the JimStim? I used a spare terminal for the MAP, every other sensor was hooked up from the 16197427.

I bought a USB to ALDL cable a few years back, knowing that between me and my friends, we'd put it to use...but I'm pretty sure it's basically an FTDI cable with an nice male ALDL connector on the end (It may be a 5v rather than TTL level cable?). I haven't done any ALDL to Arduino work yet, though it looks like others have. FYI, you can get Arduino Nano clones off Ebay for about $2...they're super convenient for quick little projects. For actual ECM chip burning, I'm using a Minipro TL866CS...less than $50 on Ebay.

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I used an Uno last week in attempts to simulate a speed sensor to bench test a cruise control module.

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A few weeks ago I was trying to troubleshoot a speedometer on a Ferrari. I tried using a function generator to drive the speedometer with a perfect square wave, but it didn't work. The problem with my test setup turned out to be that my square wave was too "clean" of a signal. The speedometer was looking for the inductive spikes in the signal, since the VSS was a magnet driving a coil. So, I ended up using the function generator to create a square wave that was driving a transistor, that was switching a coil on a relay(I was only using the coil on the relay, for the sake of putting an inductor in the circuit)...then the speedometer came to life. The resulting signal was basically a square wave, but had a spike in it that quickly decayed.

https://youtu.be/iNEZS1nCdUo

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What inputs are you missing on the JimStim?

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I was thinking something for VSS, EST, fuel pump, park/neutral, various solenoid outputs, etc. Obviously, nothing critical...just for the sake of obsessive completeness.

Wow, I wish I could keep pace with what you are doing! I love the little arduino nanos, have a half dozen or so that I pull out of the drawer and play with.

Good tip on the VSS signal, i was also using a function generator that may have caused the same issue with the cruise module.

I can offer a little tip on the fuel pump signal. Awhile ago I bought a set of 20 or so 12v LEDs on eBay for cheap. The ECM sends a +12v signal down the green/white fuel pump wire. You've likely figured out the JimStim looks for a ground signal for its FP LED. I tie an LED between the green/white wire and ground. Works great. I also used one of the 12v LEDs for an SES signal, but this time tied between +12v and the ground signal from the brown/white signal wire.