There are a few different ways that you can test your body control module (BCM). One way is to use a BCM tester, which can be found at most auto parts stores. This will allow you to test the functionality of the BCM and its various components.
Another way to test the BCM is by using a multimeter. You'll want to set the multimeter to the ohm setting and then touch the probes to the two terminals on the BCM connector. If the multimeter reads infinity, then there is an open circuit and the BCM is not functioning properly. If it reads zero, then there is a short circuit and again, the BCM is not working correctly.
Finally, you can also test the BCM by observing its output signals. Most BCMs have LED indicators that will light up when certain functions are activated. For example, if you turn on the headlights, you should see an LED light up on the BCM indicating that it has received power from the headlight switch. If you don't see this indicator light, then there may be an issue with either the headlight switch or the BCM itself.