Yes, as far as I know, the mileage is stored in the instrument cluster.
Ok, getting there. There is dedicated pin for the light on instrment cluster, have you tried hooking it to a different light? The first thing that comes to mind is the low brake fluid/hand brake on light as the connector is there on the brake fluid bottle. Take a look at my JASAPP thread, there is definition of pins (3) for the low brake fluid notificiation light and connect that to the pin on ABS module. If it lights up, you will know it is trying to send the malfunction signal. Hell, you could test it with multimeter alone for that matter. It is straightforward, I would expect it light up the indicator directly, as everything else on puma is done