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

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Grounds for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Power Distribution/SJB for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Module Communications Network for schematic and connector information.

Normal Operation 

The smart junction box (SJB) communicates with the scan tool through the medium speed controller area network (MS-CAN). Circuits VDB06 (GY/OG) (MS-CAN +) and VDB07 (VT/OG) (MS-CAN -) provide the network connection to the SJB. The SJB shares the MS-CAN with the instrument cluster (IC), the accessory protocol interface module (APIM), the HVAC module (if equipped), the audio control module (ACM), the audio digital signal processing (DSP) module (if equipped), the satellite digital audio receiver system (SDARS) module (if equipped), the driver seat module (DSM) (if equipped), the dual climate control seat module (DCSM) (if equipped), the liftgate/trunk module (LTM) (if equipped), the parking aid module (PAM) (if equipped) and the rear entertainment module (RETM) (if equipped). Voltage for the SJB is provided by circuit CDC33 (VT/GN). Circuit GD133 (BK) provides ground.

This pinpoint test is intended to diagnose the following:

• Fuse
• Wiring, terminals or connectors
• SJB

PINPOINT TEST I: THE SMART JUNCTION BOX (SJB) DOES NOT RESPOND TO THE SCAN TOOL 

1. I1 CHECK THE SJB FUSE FOR VOLTAGE 
   • Key in OFF position.
   Fig 1: Checking Circuit For Voltage
   Courtesy of FORD MOTOR CO.
   NOTE: Measurements are taken with the fuses installed.
   • Measure the voltage between the SJB fuse 5 (10A) and ground.
   • Is the voltage greater than 10 volts? 
   1. YES  : Go to  I2.
   2. NO  : VERIFY the SJB fuse 5 (10A) is OK. If OK, go to  I4.
2. I2 CHECK THE SJB GROUND CIRCUITS FOR AN OPEN 
   • Key in OFF position.
   • Disconnect: SJB C2280d
   • Measure the resistance between the SJB, harness side and ground as follows:

     Connector-Pin	Circuit
     C2280d-12	GD133 (BK)
     C2280d-8	GD133 (BK)

   • Are the resistances less than 5 ohms? 
   1. YES  : Go to  I3.
   2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the network test with the scan tool.
3. I3 CHECK THE MS-CAN CIRCUITS BETWEEN THE SJB AND THE DATA LINK CONNECTOR (DLC) FOR AN OPEN 
   • Disconnect: SJB C2280b
   Fig 2: Checking MS-CAN Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the SJB C2280b-37, circuit VDB06 (GY/OG), harness side and the DLC C251-3, circuit VDB06 (GY/OG), harness side.
   Fig 3: Checking MS-CAN Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the SJB C2280b-38, circuit VDB07 (VT/OG), harness side and the DLC C251-11, circuit VDB07 (VT/OG), harness side.
   • Are the resistances less than 5 ohms? 
   1. YES  : Go to  I4.
   2. NO  : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the network test with the scan tool.
4. I4 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.
   • Operate the system and verify the concern is still present.
   • Is the concern still present? 
   1. YES  : INSTALL a new SJB. REFER to MULTIFUNCTION ELECTRONIC MODULES article. 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.