I am using PSOC 4200 (CY8C4247LQI-BL483), where I2C SCL line is stuck low due to the nak bit received. I2C lines are pulled up using 4.7Kohm.
This is a common problem in I2C. The external device is holding SDA low, because it is out of sync. You need to manually clock it until it releases the bus. The solution is to temporarily set the IOs back to GPIO, then manually clock it until it releases. My solution is here:
You will need to adapt it to use your pins.