Checking the 4X4 control module for DTC'S - diagnostic trouble codes is what you should done . Need a factory or professional type scan tool , no an OBD2 code reader . Looking at factory service repair info. description of how it works , an testing is how to diagnose . Not guessing an throwing parts at it .
DTC B2725
The accessory switch circuit consists of 4 modes. The transfer case shift control module supplies 5 volts to the switch through the switch signal circuit. The current travels through the resistor of the currently active mode. The current on the switch signal circuit is monitored by the transfer case shift control module. The voltage on the switch signal circuit will vary depending on which mode button is pressed by the driver.
The transfer case shift control module constantly monitors the switch signal circuit to determine the condition of the accessory switch circuit.
When each of the modes are selected they complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch signal circuit to determine whether the Neutral, 2HI, 4HI, or 4LO mode was selected by the driver.

DTC C0327 Encoder Circuit Malfunction
The transfer case shift control module has 4 encoder circuits, and each circuit is supplied 12 volts. These 4 circuits are A, B, C, and P, and each circuit runs to a switch located inside the encoder/motor assembly. When a particular encoder circuit is active, the switch is closed, and the 12 volts are grounded by the switch inside the encoder.
The transfer case shift control module supplies 12 volts on all the circuits. The module can interpret the location of the transfer case shift position when the circuits are grounded.
This DTC detects a fault when it compares the shift sequence/strategy to a chart located in read only memory (ROM), within the electronic control unit (ECU), within the transfer case shift control module. This is accomplished by the module reading the different combinations of encoder signals being grounded while others remain high depending on what mode or range the transfer case is in.

DTC C0550 ECU Malfunction
At each power-up, the transfer case shift control module runs a self-test on the following functions:
• EEPROM Checksum
• ROM Checksum
• RAM Checksum
• RAM Malfunction

I suggest your take your vehicle to a qualified repair shop .