error 4042 during DFU software restore

I had the same problem. Screen was black until i plugged it into a charger from an outlet, then logo kept going on and off. Tried all teh fixes to reset and restore through itunes, but nothing worked. I found a little info on what could cause problems with an iphone rebooting and took a guess that it was the battery. Had the battery replaced and it's fixed. I checked a few forums and also called some cell phone repair shops, was told: it's the phone gone bad, it's the circuit board, it's the software. I took it to the repair shop and told the guy it I thought it was the battery. He said is was a chip, but would humor me and replace the battery to prove it wasn't the battery. Turns out, it was. It cost me $25 to get the battery replaced on an iphone 6S, but prices can vary greatly depending on the repair shop, so I'd do some calling to find out what it costs to replace a battery on your device before you decide on which shop to visit.

I had the same issue. Suddenly my iPad wasn’t charging properly. It was restarting every 2 seconds. Brought it to the Apple Store to have it checked. Battery was ok. But they couldn’t fix it (hardware issue) and offered to buy a new unit.

I ended up buying a new unit but didn’t gave up on the old one.

I brought it to someone doing micro soldering and upon opening it he found out that some component of the charging board had to be replaced. It did the trick. Cost me 159€. ;)