Repair Guide: iPhone 7 iTunes unknown error 4013 (baseband PMU)

Have you ever met 4013 error on your iPhone? If yes, do you have any idea to fix it? Here is a case, the iPhone 7 has unknown error 4013 when restore it by iTunes, and here is repair guide for it.

After we get the iPhone 7, first of all, we need to test the iPhone 7. Turn on iPhone 7, the iPhone 7 is stuck in iTunes recovery mode, it can't access the IOS systems. Next, connect iPhone 7 to the computer by iPhone lightning cable, and recover it by iTunes, but the iPhone 7 got 4013 error during the recovery process, while the iPhone 7 automatically restarts.

Based on our experience, iPhone iTunes 4013 error usually is caused by virtual welding , damaged iPhone CPU, iPhone baseband PMU and the power of the iPhone Nand flash.

Now we can check iPhone baseband PMU and the power of the iPhone Nand flash.

Connect iPhone 7 to the DC power supply, measuring the working voltage of the iPhone baseband PMU test point C5623 and C5631, the result is that the data measured of the C5623 and C5631 are normal. Now, we can confirm that the iPhone power supply of iPhone baseband PMU is normal.

Now, let's focus on the power of the iPhone Nand flash. Use QUICK 861DW hot air rework station to remove the black adhesives around the iPhone Nand flash, and then measure the voltage of the iPhone Nand flash test point C1701, C1721 and C1704. Based on the measured data, the power of the iPhone Nand flash is also normal. So, now we confirmed that the iPhone Nand flash has no problem.

Directly replace the iPhone baseband PMU, use hot air gun to remove the iPhone baseband PMU from the iPhone motherboard, and then weld the solder pad with jumper wire, next use PCB cleaner to clean the solder pad.

Apply some solder paste to the solder pad, put new iPhone baseband PMU to the right position, and then solder it by QUICK 861DW hot air rework station. After installation, cool down the iPhone motherboard for 5 minutes, and then clean it up with PCB cleaner.

Finally, install the iPhone 7, use iTunes to restore it, it goes well, no unknown error appears. Press the iPhone power button, the iPhone can boot smoothly. After entering the iOS, all functions tested are normal.