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Pinpoint Test B: No Communication With The Four-Wheel Drive (4WD) Control Module

NOTE: Conduct Steps 1 through 7 outlined in Inspection and Verification prior to performing this test.

B1 CHECK FOR COMMUNICATION TO OTHER MODULES
- Using the diagnostic tool, attempt communication with other modules on the high speed CAN.
- Does the diagnostic tool communicate with other high speed CAN modules?
Yes : GO to B2.

No : DIAGNOSE the high speed CAN communication network. REFER to MODULE COMMUNICATIONS NETWORK .
B2 CHECK POWER TO THE 4WD CONTROL MODULE
- Key in OFF position.
- Disconnect: 4WD Control Module C3253.
- Key in ON position.
- Measure the voltage between 4WD control module C3253-6, circuit 704 (DG/LG), harness side and ground; and between 4WD control module C3253-5, circuit 1003 (GY/YE), harness side and ground.
  
  Fig 1: Checking Power To 4WD Control Module
  Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
Yes : GO to B3.

No : INSPECT smart junction box (SJB) fuse 18 (10A) or 35 (5A) for an open. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
B3 CHECK THE 4WD CONTROL MODULE GROUND
- Key in OFF position.
- Measure the resistance between 4WD control module C3253-15, circuit 57 (BK), harness side and ground.
  
  Fig 2: Checking 4WD Control Module Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : REFER to MODULE COMMUNICATIONS NETWORK to continue diagnosis of the CAN circuits.

No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.