Chosen Solution
I have a 2015 MacBook Pro Retina with touch bar. One day I noticed the battery was not at 100%, even though the computer was plugged in. The battery slowly discharged down to zero and now it won’t turn on, it only makes the dead battery symbol on the screen. I have tried another charger and it makes no difference. I also removed the bottom case and disconnected the keyboad and trackpad cable and it made no difference. I also tried all the keyboard reset key patterns. It seems like parts of the board get hot when the power cable is plugged in, but still won’t power on. The fans would turn on for a few moments when I try to turn it on but that’s all.
Unplugging the trackpad and keyboard is a good start, but my approach to no power issues is usually as follows. Take off the bottom case. Disconnect the battery—both the little cable AND the T5 screw (which is actually what transmits the power to the board). Disconnect everything other than what is strictly necessary for the machine to boot up and have display. So basically leave one of the two USB C boards connected. And the display. Leave battery disconnected and use the charger to get it to boot. See if you get power at that point. If so, reconnect stuff until you no longer get power. Make sure to try both USB C board. It could also just be a bunk battery. If you still don’t get power at that point, try reconnecting keyboard and/or trackpad, but disconnecting the display to see if that’s the issue. Keyboard will facilitate fan connection to the board so you could tell if it’s getting power that way. Or trackpad would give you haptic feedback, which is usually a good indicator that it’s booting if that’s clicking consistently. If still no power at that point, more than likely its a board issue. It’s possible it’s still repairable even if that’s the case, just will be trickier.
