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Pinpoint Test Aa: P0A71, P0A74, P0A77

  1. NOTE: The Secondary Inverter System Controller (S-ISC) is referred to as the SOBDMB (Secondary On-Board Diagnostic Control Module B) in the scan tool.

    Normal Operation and Fault Conditions 

    REFER to: Front Electric Drive Assembly - System Operation and Component Description .

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    SOBDMB P0A71:00 Generator Phase U Current High: No Sub Type Information This DTC sets when the U phase current is outside of the normal range.
    SOBDMB P0A74:00 Generator Phase V Current High: No Sub Type Information This DTC sets when the V phase current is outside of the normal range.
    SOBDMB P0A77:00 Generator Phase W Current High: No Sub Type Information This DTC sets when the W phase current is outside of the normal range.

    Possible Sources 

    • Wiring, terminals or connectors
    • Low voltage wiring
    • Other Secondary Inverter System Controller (S-ISC) DTCs
    • Secondary Inverter System Controller (S-ISC) calibration
    • Secondary Inverter System Controller (S-ISC) SEDID block programming
    • Front electric drive assembly

  2. AA1 READ THE SECONDARY INVERTER SYSTEM CONTROLLER (S-ISC) DIAGNOSTIC TROUBLE CODES (DTCS)

    NOTE: Wiring overlays or repinning of circuits are NOT appropriate for DTCs P0A71, P0A74 or P0A77 due to risk of hardware damage.

    • Using a diagnostic scan tool, retrieve the Secondary Inverter System Controller (S-ISC) CMDTCs.

    Are P0A71, P0A74 or P0A77 the only DTCs present? 

    Yes  GO to  AA2
    No  DIAGNOSE all other Secondary Inverter System Controller (S-ISC) DTCs. REFER to Diagnostic Trouble Code (DTC) Chart .

  3. AA2 CHECK THE SECONDARY INVERTER SYSTEM CONTROLLER (S-ISC) CALIBRATION LEVEL

    • Verify the Secondary Inverter System Controller (S-ISC) is at the latest calibration level.

    Is the Secondary Inverter System Controller (S-ISC) at the latest calibration level? 

    Yes  GO to  AA3
    No  UPDATE the Secondary Inverter System Controller (S-ISC) to the latest calibration level.

  4. AA3 VERIFY THE SECONDARY INVERTER SYSTEM CONTROLLER (S-ISC) SEDID BLOCK HAS BEEN PROGRAMMED CORRECTLY

    NOTE: To avoid confusion the SEDID information corresponds with the primary (rear) electric drive system and is stored in the primary ISC (SOBDM-C). The SEDID stores similar but different information which corresponds with the secondary (front) electric drive system and is stored in the S-ISC (SOBDM-B).

    • Verify the Secondary Inverter System Controller (S-ISC) SEDID block has been programmed correctly. Refer to Module Reprogramming on the scan tool.

    Has the SEDID block been successfully programmed? 

    Yes  GO to  AA4
    No  CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, reflash the Secondary Inverter System Controller (S-ISC) SEDID block.

  5. AA4 VISUAL INSPECTION OF THE LOW VOLTAGE SYSTEM

    • Ignition OFF.

    • Visually inspect all the low voltage cables.

    • Make sure all the low voltage connectors are correctly and securely connected.

    • Examine all the low voltage cables and connectors for damaged, burned or overheated insulation and loose or broken conditions.

    Is a concern present? 

    Yes  REPAIR as necessary. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs and REPEAT the self-test.
    No  GO to  AA5

  6. AA5 CHECK THE RESOLVER HARNESS CIRCUITS FOR AN OPEN

    • Disconnect Secondary Inverter System Controller (S-ISC) C1458A.

    • Disconnect Front electic drive assembly C1280.

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      C1280-9
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A1
      C1280-8
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-B1
      C1280-5
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A3
      C1280-3
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-B3
      C1280-4
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A2
      C1280-2
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-B2

    Is the resistance less than 3 ohms? 

    Yes  GO to  AA6
    No  With the aid of the OEM WIRING DIAGRAMS , REPAIR the open circuit. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  7. AA6 CHECK THE RESOLVER HARNESS CIRCUITS FOR A SHORT TOGETHER

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      C1280-9
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1280-All pins except pin 8
      C1280-8
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1280-All pins except pin 9
      C1280-5
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1280-All pins except pin 3
      C1280-3
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1280-All pins except pin 5
      C1280-4
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1280-All pins except pin 2
      C1280-2
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C4555A-All pins except pin 4

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA7
    No  REPLACE the harness. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  8. AA7 CHECK THE RESOLVER HARNESS CIRCUITS FOR A SHORT TO GROUND

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      C1280-9
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-8
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-5
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-3
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-4
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-2
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA8
    No  REPLACE the harness. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  9. AA8 CHECK THE GENERATOR RESOLVER CIRCUITS FOR A SHORT TO VOLTAGE

    • Ignition ON.

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      C1280-9
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-8
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-5
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-3
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-4
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground
      C1280-2
      GFD609107Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is any voltage present? 

    Yes  REPLACE the harness. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.
    No  GO to  AA9

  10. AA9 CHECK THE RESOLVER CIRCUITS FOR A SHORT TO THE EXTERNAL CABLE SHIELD

    • Ignition OFF.

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      C1458A-A1
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4
      C1458A-B1
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4
      C1458A-A3
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4
      C1458A-B3
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4
      C1458A-A2
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4
      C1458A-B2
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458A-A4

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA10
    No  REPLACE the harness. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  11. AA10 CHECK THE FRONT ELECTRIC GENERATOR RESOLVER RESISTANCES

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 4, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 2, component side

    Is the resistance between 11.2 and 16.8 ohms? 

    Yes  GO to  AA11
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  12. AA11 CHECK THE FRONT ELECTRIC GENERATOR RESOLVER RESISTANCES

    • Ignition OFF.

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 5, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 3, component side

    Is the resistance between 11.6 and 17.4 ohms? 

    Yes  GO to  AA12
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  13. AA12 CHECK THE FRONT ELECTRIC GENERATOR RESISTANCES

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 9, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 8, component side

    Is the resistance between 7.6 and 11.4 ohms? 

    Yes  GO to  AA13
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  14. AA13 CHECK THE GENERATOR RESOLVER GR1 CIRCUIT FOR A SHORT

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 9, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 all pins except pin 8, component side

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA14
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  15. AA14 CHECK THE GENERATOR RESOLVER GS1 CIRCUIT FOR A SHORT

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 5, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 all pins except pin 3, component side

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA15
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  16. AA15 CHECK THE RESOLVER GS2 CIRCUIT FOR A SHORT

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 4, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 all pins except pin 2, component side

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA17
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  17. AA16 CHECK THE RESOLVER FOR A SHORT TO GROUND

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 9, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 8, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 5, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 3, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 4, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD609110Courtesy of FORD MOTOR COMPANY

      C1280 pin 2, component side
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA17
    No  INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  18. AA17 VISUAL INSPECTION OF THE HIGH VOLTAGE SYSTEM

    • Examine all the high voltage connections for damage and loose or broken conditions.

    Is a concern present? 

    Yes  REPAIR as necessary. CLEAR the Secondary Inverter System Controller (S-ISC) DTCs and REPEAT the self-test.
    No  GO to  AA18

  19. AA18 CHECK THE PHASE WIRING FOR AN OPEN

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD608930Courtesy of FORD MOTOR COMPANY
      GFD608930Courtesy of FORD MOTOR COMPANY

    Is the resistance less than 3 ohms? 

    Yes  GO to  AA20
    No  INSTALL a new high voltage cable between the Secondary Inverter System Controller (S-ISC) and the front electric drive assembly. REFER to: High Voltage Battery Cables
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  20. AA19 CHECK THE PHASE WIRING FOR A SHORT TO SHIELD

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458C Cable Shield
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458C Cable Shield
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 C1458C Cable Shield

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA20
    No  INSTALL a new high voltage cable between the Secondary Inverter System Controller (S-ISC) and the front electric drive assembly. REFER to: High Voltage Battery Cables
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  21. AA20 CHECK THE PHASE WIRING FOR A SHORT TO GROUND

    NOTE: Use a chassis ground for the following test step.

    • Connect C1458C.

    • Measure and record:
      Positive Lead Measurement / Action Negative Lead
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground
      GFD608930Courtesy of FORD MOTOR COMPANY
      		 Ground

    Is the resistance greater than 10K ohms? 

    Yes  GO to  AA21
    No  INSTALL a new high voltage cable between the Secondary Inverter System Controller (S-ISC) and the front electric drive assembly. REFER to: High Voltage Battery Cables
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test.

  22. AA21 CHECK FOR CORRECT SECONDARY INVERTER SYSTEM CONTROLLER (S-ISC) OPERATION

    • Ignition OFF.

    • Disconnect and inspect all Secondary Inverter System Controller (S-ISC) connectors.

    • Repair:

      • corrosion (install new connector or terminals - clean module pins)
      • damaged or bent pins - install new terminals/pins
      • pushed-out pins - install new pins as necessary

    • Reconnect all previously disconnected connectors. Make sure they all seat and latch correctly.

    • Ignition ON.

    • CLEAR the Secondary Inverter System Controller (S-ISC) DTCs.

    • Ignition OFF.

    • Start the engine.

    • Using a diagnostic scan tool, run the Secondary Inverter System Controller (S-ISC) self-test.

    Are any DTCs present? 

    Yes  For DTCs P0A71, P0A74 or P0A77 only, INSTALL a new front electric drive assembly. REFER to: Front Electric Drive Assembly 
    CLEAR the Secondary Inverter System Controller (S-ISC) DTCs. REPEAT the self-test. For all other DTCs, DIAGNOSE all other Secondary Inverter System Controller (S-ISC) DTCs. REFER to Diagnostic Trouble Code (DTC) Chart .
    No  The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.
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