What is error 4042 when trying to restore iphone - apple logo blinking on and off when connected to outlet?

Symptom: At first my phone screen was completely black. then I plugged it into a charger from an outlet and the apple logo would appear than disappear. Then I tried all the 'fixes' to upgrade and restore through itunes. no help at all. Being a computer geek by trade, looking at the symptoms and what little information I could find about what can prevent an iphone from rebooting I took a guess that it was the battery or the port. Turns out it was the battery. So if you are having this issue, I would suggest first calling around to see what repair places charge to replace a battery ( I paid $25 to have an iphone 6s battery replaced) and then going to the one that is reasonable. FYI - they might try to tell you it's not the battery like I was told, but ask if they can at least attempt the battery install. If it's not the battery, they can take it right back out and if they charge you anything at all it shouldn't be more than $5 to test out the theory. however, it could very well fix your problem. I couldn't get any answers from apple support and most iphone fix it places was telling me the phone was dead, there was problems with some chips, the circuit board was bad, etc.... Hope this helps some of the people who like me was banging my head against the wall trying to find a solution.