How To Fix iPhone 4S That Is Bootlooping With iTunes Error 29

Problem description
If the iPhone 4S is Bootloopin and you flash an update that causes Error 29 (failing at 60% with iTunes flash)

Or 3u Tools Easy Flash failing at 80% (Updating GasGauge).

Then follow these steps to resolve it

Symptoms

 * Bootlooping
 * Flashing Apple Logo
 * Restarting with the Apple Logo Flashing
 * Failing an update with error 29
 * Failing at about 60% on iTunes flash
 * Failing at 80% on 3u tools with the message "Updating GasGauge"

Diagnostic Steps

 * This is often caused by a low-quality replacement battery, use an original battery.
 * Check for missing components near the battery connector. See Figure 1.



Repair Steps

 * A missing R61 resistor near the battery connector can cause this. Replace it.
 * For data only, you can also try running a jumper across the pads, to recreate the connection. See Figure 2.