do you have voltage at the bulb when in low beam? if you can easily pull your switch, run a continuity test between power and low beam out and cycle the switch. If that's good, check the wiring at various points between the switch and the light.
electrical can be the most challenging thing to troubleshoot
X2 on that. I have been doing this almost 22Yrs & still get stumpped more than I would like to
Dealing with all the New Bells & Whisels there installing into these new cars can really throw you for a loop when trying to figure out issues
Screw Ohms Law. If I had a perfect understanding of all this Electral "CRAP" I would be building Rockets
Pin Fit issues were one of many issues in the ZJ. It's great that you have known good spare parts to eliminate the bad part But after the spare parts run out & the issue still exsists then the next step is a good visual inspection of all the small pins for discoloration (heat damage) witch tells you of a poor conection. Inspect both (conector & part) because sometimes you can't always see the heat damage on both sides. Theres also Grounds & other thing to look into so the bottom line is not to over look anything. Good Luck!!!