I don't know if this topic belongs in here, but the airbag light is on, steady, with no tones. I want to try to extinguish it before ripping into the removal/testing of the module. Can I earth (short) the airbag diagnostic pin to say the engine earth pin, or does it need to be to a proper earth, say battery neg?

AFAIK, removal of the module means dashboard removal

Read the sticky in the interior section.