BDM test Fixture for P01 and P59 Powertrain Control Modules, as used in a variety of GM cars and trucks in the late 1990s to early-mid 2000s.

thingiverse

If you are working on software to tune the engines in these cars you run the risk of bricking your PCM. There's a pretty good chance that you can un-brick it using a debugging device (link below). Traditionally, users would solder directly to the solder dots on the back of the circuit boad, but this approach was inspired by David Braley, here: https://pcmhacking.net/forums/viewtopic.php?f=42&t=6215&sid=4de2e1f85d6ee0f6bac79f82dafcbed4 He built his test fixture jig with a mill. I only have an FDM printer... so he sent a drawing that had all of the key dimensions, and I turned that into something that I could print. Fortunately it was just barely small enough to fit in my new Prusa I3 MK3S. You'll need to add test pins (also known as "pogo pins" to mount in it. I used these... https://smile.amazon.com/gp/product/B07HC5VKVT/ ...but any similar product will do. If the outside diameter is not 0.9mm you should adjust the hole size in the OpenScad file accordingly. In fact you might want to make the hole size just a tiny tiny bit smaller if you use the same pins I did. One of them needs a push once in a while. Most importantly, you'll also need a USB--BDM-NT device from https://www.usbjtag.com/zenshop/index.php. Solder up, and you should be able to reprogram your PCM. If you read the source code of the OpenScad file, you'll see how to make it print small test fixtures to for trial-and error experiments to find the right diameter for the pin holes. You want them to fit snug, so that they stay in place under load, but you don't want them to fit so loosely that they move away from the cricuit build and lose contact. Personally, I printed two test parts to get the diameter just right. Not shown here: you'll have to solder this up to the USB-DBM device, and then hook that up to your computer. This has been proven with both P01 (512kb) and P59 (1mb) PCMs.