Opcom Free4all Portable -

Right-click the device > Properties > Port Settings > Advanced. Change the COM port number to COM 3, 4, or 5 (Opcom 1.39 prefers low numbers). Also set Latency Timer to "1" (very important for stable data).

You own a 1995–2015 GM car, you are comfortable with driver hacking, and you want to program your own keys. Avoid it if: You own a new car, you are not technically savvy, or you cannot afford to potentially replace an ECU. opcom free4all portable

Plug in the Opcom box. Open Device Manager. You will see an unknown device with a yellow exclamation. Manually point the driver installer to the "Drivers" folder in your Portable package. Right-click the device > Properties > Port Settings

(8.5/10 for value; 2/10 for safety)