Ramzi,

CAN communication fault will start with the troubleshooting port at the steer column. Pins A and B are CAN Hi and Low. With battery disconnected check resistance between pins A and B, should read about 60 ohms. Can be from 58 to 62. If you have FOC2 controllers you may read 40 ohms. Connect battery and check for voltage between pins A and C, B and C. They both should read about 2.5 volts. Can be between 1.8 to 2.6. Both should total about 4.5 volts.
Disconnect the VSM connector CPS2 and measure voltage between socket 35 and B(-).
Is voltage 12 ± 1.5 Vdc?
YES: Proceed to Step 2.
NO: Inspect circuit 200A and 200M for open or short. Inspect connector CRP52-55 for loose, damaged, or
corroded terminals.
2. Measure voltage between socket 35 and the VSM connector CPS2, socket 2.
Is voltage 12 ± 1.5 Vdc?
YES: Proceed to CAUSE C.
NO: Inspect 013-A for open or short

Cause C is check the CDF version for the truck using PC Service tool. You will need a dealer to complete. Should all checks good, replace controller. Good Luck.