ad5860 — I2C bus

AD5860 is the haptic motor driver; its signal runs through the charging port assembly. iFixit recommends starting with the charging flex (cases solved this way), as the Taptic itself is not necessarily at fault.

iPhone

Charging port flex (link to the AD5860 haptic driver), then Taptic Engine

Medium confidenceVerified sourceI2C bus

First check

Test with the charging flex disconnected (boot with the button / wireless charging), then with a known-good flex.

Sources