My car won't start and it says system malfunction

Hi this is Dusty, I'm one of the auto experts on RepairPal's Car Genius team. I’m sorry to hear about the trouble you’re having with your 2021 Nissan Sentra. The “system malfunction” warning light can be triggered by various issues. Even though you’ve had the battery tested and it came out fine, there could still be an issue with the battery, the battery terminals, or another component in the starting system. I've seen failing batteries give a false positive test result, usually this inconsistency is due to a bad cell in the battery. Since the problem seems to get better when you jump-start the car, it’s highly likely that it is related to the battery or electrical system. However, it’s best to have a professional diagnose the issue to be sure. I hope this helps, and your car gets back to normal soon! If you have any questions, give us a call at (877) 913-1554