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Pinpoint Test D: The Smart Junction Box (SJB) Does Not Respond To The Scan Tool

WARNING: This page is about a different car, the 2009 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. D1 CHECK THE MS-CAN TERMINATION RESISTANCE 
    • Key in OFF position.
      • NOTE: Failure to disconnect the battery will result in false resistance readings.
    • Disconnect the battery ground cable.
      • Fig 1: Checking MS-CAN (+) & MS-CAN (-) Circuits For A Short
      GF0001410Courtesy of FORD MOTOR CO.
    • Measure the resistance between the DLC C251-3, circuit 1847 (WH/OG), harness side and the DLC C251-11, circuit 1848 (PK/OG), harness side.
    • Is the resistance between 54 and 66 ohms? 
    1. YES  : Go to  D3.
    2. NO  : Go to  D2.
  2. D2 CHECK THE MS-CAN CIRCUITS BETWEEN THE SJB AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN 
    • Disconnect: SJB C2280b
      • Fig 2: Measuring Resistance Between SJB C2280B-50 And DLC C251-3
      GF0016186Courtesy of FORD MOTOR CO.
    • Measure the resistance between the SJB C2280b-50, circuit 1847 (WH/OG), harness side and the DLC C251-3, circuit 1847 (WH/OG), harness side.
      • Fig 3: Measuring Resistance Between SJB C2280B-51 And DLC C251-11
      GF0016187Courtesy of FORD MOTOR CO.
    • Measure the resistance between the SJB C2280b-51, circuit 1848 (PK/OG), harness side and the DLC C251-11, circuit 1848 (PK/OG), harness side.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  D3.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  3. D3 CHECK THE SJB VOLTAGE SUPPLY CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Disconnect: SJB C2280h
    • Connect: Battery Ground Cable
    • Key in ON position.
      • Fig 4: Checking SJB Voltage Supply Circuits For An Open
      GF0046567Courtesy of FORD MOTOR CO.
    • Measure the voltage between the SJB, harness side and ground as follows:
      Connector-Pin Circuit
      C2280h-11 1523 (DG)
      C2280h-31 905 (GY/LB)
      C2280h-32 1052 (TN/BK)
    • Are the voltages greater than 10 volts? 
    1. YES  : Go to  D4.
    2. NO  : VERIFY the bussed electrical center (BEC) fuse(s) 59 (30A), 63 (30A) and 67 (30A) are OK. If OK, REPAIR the circuit in question. If not OK, REFER to the appropriate SYSTEM WIRING DIAGRAMS to IDENTIFY the possible causes of the short circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
  4. D4 CHECK THE SJB GROUND CIRCUITS FOR AN OPEN 
    • Key in OFF position.
      • Fig 5: Checking SJB Ground Circuits For An Open
      GF0016184Courtesy of FORD MOTOR CO.
    • Measure the resistance between the SJB C2280h-8, circuit 1205 (BK), harness side and ground; and between the SJB C2280h-22, circuit 1205 (BK), harness side and ground.
    • Are the resistances less than 5 ohms? 
    1. YES  : Go to  D5.
    2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
  5. D5 CHECK FOR CORRECT SJB OPERATION 
    • Disconnect all the SJB connectors.
    • Check for:
      • corrosion
      • damaged pins
      • pushed-out pins
    • Connect all the SJB connectors and make sure they seat correctly.
    • Repeat the network test.
    • Does the SJB still fail to communicate to the scan tool? 
    1. YES  : INSTALL a new SJB. REFER to MULTIFUNCTION ELECTRONIC MODULES . CLEAR the DTCs. REPEAT the network test with the scan tool.
    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 network test with the scan tool.
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