Ok guys I need help here. I’ve owned my 2007 m35x for many many years and since I can remember I’ve have issues every single time I replace a battery. Historically the key won’t get recognized, it won’t start, etc while still having full functionality with headlights, door locks, etc. most of these issues self cleared within a day or two. Maybe a year ago I cleaned my terminals and car was out of service for over a month. It simply wouldn’t come back to life and my mechanic ended up replacing 3 fuse boxes one of them being the ipdm behind the battery and fired up like a charm. Todays issue however is similar but different. I was about to wire an amplifier and disconnected the negative terminal. Realized I was missing parts so 5 min later the terminal was reinstalled and here we go again… no start… this time the cluster is dead… only thing that appears is the high beam indicator when lights are turned on… ignition does nothing… I’ve researched all night and many say it’s ipdm but there’s no way I have to replace this again… can’t be… they are hard to find! Anybody dealt with this? Troubleshooting guide? Anything helps.

The I-Key Unit (located in the kick panel next to the parking brake pedal) is in charge of all of that, and it must not be booting up properly after disconnection. The BCM and IPDM are involved too, but the fact that the lights work means both of those are alive and online. The I-Key Unit has non-volatile memory onboard and disconnecting the power shouldn't affect it like that, so I'd say it's likely yours is bad.

Hmm… I am 95% sure I replaced this last year when I replaced the other fuse holders… I will give it a shot