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Pinpoint Test E: Controller Area Network (Can) Communications Bus Fault

NOTE: Conduct Steps 1 through 10 outlined in Inspection and Verification prior to carrying out this test.
  1. E1 CHECK THE HIGH SPEED CAN CIRCUITS BETWEEN THE DLC AND THE 4X4 CONTROL MODULE FOR AN OPEN 
    • Key in OFF position.
      • Fig 1: Checking High Speed Can Circuits Between DLC And 4X4 Control Module For An Open
      GF0030112Courtesy of FORD MOTOR CO.
    • Measure the resistance between 4X4 control module C3253-4, circuit VDB04 (WH/BU), harness side and DLC C251-6, circuit VDB04 (WH/BU), harness side; and between 4X4 control module C3253-12, circuit VDB05 (WH), harness side and DLC C251-14, circuit VDB05 (WH), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  E2.
    2. NO  : REPAIR the circuit(s). CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  2. E2 CHECK THE HIGH SPEED CAN CIRCUITS FOR A SHORT TO GROUND 
    • Key in OFF position.
      • Fig 2: Checking High Speed Can Circuits For A Short To Ground
      GF0030113Courtesy of FORD MOTOR CO.
    • Measure the resistance between 4X4 control module C3253-4, circuit VDB04 (WH/BU), harness side and ground; and between 4X4 control module C3253-12, circuit VDB05 (WH), harness side and ground.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  E3.
    2. NO  : REPAIR the circuit(s). CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  3. E3 CHECK THE RESISTANCE BETWEEN HIGH SPEED CAN CIRCUITS 
    • Key in OFF position.
      • Fig 3: Checking Resistance Between High Speed CAN Circuits
      GF0030114Courtesy of FORD MOTOR CO.
      NOTE: The powertrain control module (PCM) and the instrument cluster (IC) must be connected and operating correctly to obtain the correct resistance between the high speed controller area network (HS-CAN) circuits.
    • Measure the resistance between 4X4 control module C3253-4 circuit VDB04 (WH/BU) harness side and 4X4 control module C3253-12 circuit VDB05 (WH) harness side.
    • Is the resistance 60 ohms (± 5 ohms)? 
    1. YES  : Go to  E4.
    2. NO  : REPAIR the circuit(s). CLEAR the DTCs. REPEAT the self-test. CARRY OUT the data link diagnostics test.
  4. E4 CHECK FOR DTCs U0100 AND U0121 SET TOGETHER 
    • Carry out the 4X4 control module self-test.
    • Review the results of the 4X4 control module self-test.
    • Are at least DTCs U0100 and U0121 set together? 
    1. YES  : REFER to MODULE COMMUNICATIONS NETWORK to continue diagnosis of the communications network.
    2. NO  : Go to  E5.
  5. E5 CHECK FOR DTC U0100 
    • Refer to the results of the 4X4 control module self-test.
    • Is DTC U0100 set? 
    1. YES  : The PCM is not sending any data to the 4X4 control module. REFER to the Introduction - Gasoline Engines for additional PCM diagnosis.
    2. NO  : Go to  E6.
  6. E6 CHECK FOR DTC U0101 
    • Refer to the results of the 4X4 control module self-test.
    • Is DTC U0101 present? 
    1. YES  : The TCM is not sending any data to the 4X4 control module. REFER to AUTOMATIC TRANSAXLE/TRANSMISSION - 6 SPEED or AUTOMATIC TRANSAXLE/TRANSMISSION - FNR5 for additional TCM diagnosis.
    2. NO  : Go to  E7.
  7. E7 CHECK FOR DTC U0121 
    • Refer to the results of the 4X4 control module self-test.
    • Is DTC U0121 set? 
    1. YES  : The ABS module is not sending any data to the 4X4 control module. REFER to VEHICLE DYNAMIC SYSTEMS for additional ABS diagnosis.
    2. NO  : Go to  E8.
  8. E8 CHECK FOR CORRECT 4X4 CONTROL MODULE OPERATION 
    • Disconnect the 4X4 control module.
    • Check the harness and component side connectors for:
      • corrosion.
      • pushed-out/bent pins.
    • Connect the 4X4 control module and make sure it seats correctly.
    • Operate the system and determine if the concern is still present.
    • Is the concern still present? 
    1. YES  : INSTALL a new 4X4 control module. REFER to 4X4 Control Module . CLEAR the DTCs. REPEAT the self-test.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.
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