Hi,

It's 2025 and I have a 2007 G35. I am having the same issues. Car totally died out of nowhere about 3 weeks ago so I had the alternator and battery replaced (both new). Brake & Battery lights came on while starting up and would disappear once I hit 2000RPM. However, today the lights came on while I was driving and stopped at a stoplight and this time they did not turn off. Car felt totally fine driving. I'll check the groundings when possible, but I work today and can't get to the mechanic for 2 more days. I have a warranty on the parts. Any other tips?

 

Can be lots of things; Faulty 'new' alternator, wrong type of alternator, bad pigtail plug to the alternator (power steering fluid drips onto it), grounds, battery terminals, BCM, BCM plugs, instrument cluster or it's plugs.
If your brake light is on, it means the brake fluid is low. Battery light means alternator is not charging properly or the ECM is not reading and/or able to control it. ECM controls the charging meanwhile, BCM controls the lights on the dash. Had an 07 and sold it to a pack of horny teenagers..