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Home >> Lincoln >> 2018 >> Navigator Select, 4WD >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> RCM Guided Routine Testing -- (3 Of 4) >> Pinpoint Tests >> Pinpoint Test BE: CAN Bus Failure >> Possible Causes
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Possible Causes

NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough inspection and verification before proceeding with the pinpoint test.
NOTE: SRS components should only be disconnected or reconnected when instructed to do so within a pinpoint test step. Failure to follow this instruction may result in incorrect diagnosis of the SRS.
NOTE: Always make sure the correct SRS component is being installed. Parts released for other vehicles may not be compatible even if they appear physically similar. Check the part number listed in the parts catalog to make sure the correct component is being installed. If an incorrect SRS component is installed, DTCs may set.
NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
Fig 1: Restraint Control Module-B (RCM-B) Connector End View (C310B)
G12765534Courtesy of FORD MOTOR CO.
Harness Side

Circuit Pin
  1. BE1: CHECK THE COMMUNICATION NETWORK 
    WARNING: Before beginning any service procedure in this article, refer to Safety Warnings in General Information article. Failure to follow this instruction may result in serious personal injury. REFER to Pyrotechnic Device Health and Safety Precautions in General Information article
    • Ignition ON, engine OFF.
    • Using a diagnostic scan tool, carry out a network test.
    • Does any modules other than the RCM fail the network test? 
      Yes No
      DIAGNOSE the HS-CAN fault. If only the RCM failed the network test, Go to  BE2.
      If all modules passed the network test, including the RCM, the fault has become intermittent, Go to  BE5.
      For all others,
      No fault found.
  2. BE2: CHECK THE HIGH SPEED CONTROLLER AREA NETWORK (HS-CAN) CIRCUIT AT THE RCM FOR AN OPEN 
    • Ignition OFF.
    • Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering in Supplemental Restraint System article.
    • RCM_A connector disconnected. (C310A)
    • RCM_B connector disconnected. (C310B)
    • Measure the resistance between:
      (+) RCM_B (C310B) Connector, Harness Side (-) DLC Connector, Harness Side
      HS-CAN1 - HS-CAN1 -
      HS-CAN1 + HS-CAN1 +
    • Are the resistances less than 3 ohms? 
      Yes No
      Go to  BE3. REPAIR the circuit,
      Go to  BE6.
  3. BE3: CONFIRM THE RCM FAULT 
    NOTE: Make sure all SRS components and the RCM electrical connectors are connected before carrying out the self-test. If not, DTCs are recorded.
    • Ignition OFF.
    • Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering in Supplemental Restraint System article.
    • Prior to reconnecting any previously disconnected SRS component:
      • inspect connector(s) (including any inline connectors) for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
      • inspect wire harness for any damaged, pinched, cut or pierced wires.
      • inspect the RCM electrical connectors and the Connector Position Assurance (CPA) levers/locks for correct operation.
      • repair any concerns found. Refer to OEM GROUND DISTRIBUTION article, for schematic and connector information.
    • Install the driver airbag (if previously removed). Refer to the appropriate Removal and Installation procedure in Supplemental Restraint System article.
    • RCM_A connector connected. (C310A) Make sure it seats and latches correctly.
    • RCM_B connector connected. (C310B) Make sure it seats and latches correctly.
    • Repower the SRS. Do not prove out the SRS at this time. Refer to Supplemental Restraint System (SRS) Repowering in Supplemental Restraint System article.
    • Ignition ON, engine OFF.
    • Carry out the RCM self-test.
    • Is the original DTC retrieved on-demand during self-test? 
      Yes No
      Go to  BE4. In the process of diagnosing the fault, the fault condition has become intermittent. Do not install any new SRS components at this time.
      Install SRS components only when directed to do so in the pinpoint test.
      Go to  BE5.
  4. BE4: CONFIRM THE REPAIR 
    • Ignition OFF.
    • CHECK OASIS for any applicable TSBs.
      • If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions.
      • If no TSBs address this concern, INSTALL a new RCM. Refer to the appropriate Removal and Installation procedure in Supplemental Restraint System article.

    INSTALL a new RCM.

    Reconnect all previously disconnected SRS components and repower the SRS. REFER to the Supplemental Restraint System (SRS) Repowering in the General Procedures portion of Supplemental Restraint System article.

    Carry out the OCSM and RCM self-test and record DTCs if present. Do not clear any DTCs until all DTCs have been resolved. DIAGNOSE and REPAIR the RCM and/or OCSM DTCs.

    Carry out the OCSM and RCM self-test and record DTCs if present. Do not clear any DTCs until all DTCs have been resolved.

    If any SRS DTCs are retrieved, DO NOT clear any DTCs until all DTCs have been resolved. DIAGNOSE and REPAIR the RCM and/or OCSM DTCs.

    If no DTCs are retrieved on-demand, the repair is complete. RETURN the vehicle to the customer.

  5. BE5: CHECK THE HARNESS AND CONNECTORS 
    • Ignition OFF.
    • Depower the SRS. Refer to Supplemental Restraint System (SRS) Depowering in Supplemental Restraint System article.
    • RCM_A connector disconnected. (C310A)
    • RCM_B connector disconnected. (C310B)
    • Inspect the RCM electrical connectors and the Connector Position Assurance (CPA) levers/locks for correct operation.
    • Inspect the RCM electrical connectors for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • Inspect wire harnesses for any damaged, pinched, cut or pierced wires.
    • Are any concerns found? 
      Yes No
      REPAIR as necessary,
      Go to  BE6.      		 Go to  BE6.
  6. BE6: CHECK FOR ADDITIONAL SRS DIAGNOSTIC TROUBLE CODES (DTCS) 
    WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.
    • Ignition OFF.
    • Reconnect all SRS components (if previously disconnected).
    • Repower the SRS. Do not prove out the SRS at this time. Refer to Supplemental Restraint System (SRS) Repowering in Supplemental Restraint System article.
    • Ignition ON, engine OFF.
      NOTE: When selecting Restraints from the Self Test menu, DTCs are retrieved from the RCM and OCSM.
    • Carry out the RCM self-test.
    • Are any RCM and/or OCSM DTCs retrieved on-demand during self-test? 
      Yes No
      Do not clear any DTCs until all DTCs have been resolved. REFER to the appropriate procedure in Supplemental Restraint System article. CLEAR all RCM and OCSM CMDTCs. PROVE OUT the SRS. The repair is complete. RETURN the vehicle to the customer.
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