Original post by: Rany ,
I detect more than one issue with your phone. First, the power button is not working properly, which is why you have to plug your iPhone into a charger or computer to get it to start. To fix this, you'll have to replace the PMV cable using this [guide|10792|guide] or ask Apple to do it for you because for this particular issue there is a repair program that extends beyond the 1-year standard warranty. Contact Apple to see if you are eligible. 2nd, you probably have an issue with your U2 IC as you guessed. But to rule all other possibilities, you can try to charge with a known good cable and charger, then try replacing the battery and finally the charging dock. A good way to tell it's that pesky IC is by replacing the battery. If the phone works until the new battery has discharged and the issues returns, it is a board problem (probably that IC) and you'd better have Apple replace the phone by paying a difference, or have a trained technician repair it for you (try asking jessabethany here on iFixit, her email is on her profile). Note that if you try to work on the phone yourself, Apple May refuse to replace your phone even if it is for a difference, and may refuse to replace your PowerMuteVolune cable in case you are eligible for the free replacement of that part.