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Home >> Ford >> 2006 >> Focus ZX5 SE, Standard >> Repair and Diagnosis >> Restraints >> Air Bag, SRS >> Supplemental Inflatable Restraint System >> Diagnosis And Testing >> Pinpoint Tests - Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) >> Pinpoint Tests >> Pinpoint Test BK: DTC U0073 - Control Module Communication Bus Off >> Pinpoint Test Bk: Control Module Communication Bus Off

Pinpoint Test Bk: Control Module Communication Bus Off

NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough Inspection and Verification before proceeding with the Pinpoint Test.
  1. BK1 CHECK FOR CONTINUOUS AND ON-DEMAND DTCs 
    WARNING: Restraint system diagnostic tools are for service only. Tools must be removed prior to operating the vehicle over the road. Failure to remove restraint system diagnostic tools could result in injury and possible violation of vehicle safety standards.
    WARNING: Never probe the connectors on the air bag module. Doing so can result in air bag deployment, which can result in personal injury.
    WARNING: The safety belt pretensioner is a pyrotechnic device. Always wear safety glasses when repairing an air bag equipped vehicle and when handling a safety belt buckle pretensioner or safety belt retractor pretensioner. Never probe a pretensioner electrical connector. Doing so could result in pretensioner or air bag deployment and could result in personal injury.
    NOTE: After diagnosing or repairing an SRS, the restraint system diagnostic tools must be removed before operating the vehicle over the road. 
    NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
    • Enter the following diagnostic mode on the scan tool: Retrieve/Record Continuous DTCs.
    • Was DTC U0073 retrieved during the Retrieve/Record Continuous DTCs? 

    Yes  : GO to  BK2.

    No  : The fault condition is not present at this time. GO to  BK6.

  2. BK2 CHECK THE HS-CAN CIRCUITS FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Depower the system. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING  in this article.
    • While monitoring the meter, attempt to recreate the hard fault by flexing the wire harness and measure the resistance between DLC C251-6, circuit 4-EC7 (GY/RD), harness side and ground; and between DLC C251-14, circuit 5-EC7 (BU/RD), harness side and ground.
      Fig 1: Checking HS-CAN Circuits For Short To Ground
      G04654976Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms while flexing the wire harness? 

    Yes  : GO to  BK3.

    No  : REPAIR circuit 4-EC7 (GY/RD) or circuit 5-EC7 (BU/RD) as necessary. GO to  BK6.

  3. BK3 CHECK THE HS-CAN CIRCUITS FOR VOLTAGE 
    • Disconnect: RCM C2041a and C2041b.
    • Repower the system. Do not  prove out the system at this time. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING  in this article.
    • Key in ON position.
    • While monitoring the meter, attempt to recreate the hard fault by flexing the wire harness and measure the voltage between DLC C251-6, circuit 4-EC7 (GY/RD), and ground; and between DLC C251-14, circuit 5-EC7 (BU/RD), and ground.
      Fig 2: Checking HS-CAN Circuits For Voltage
      G04654977Courtesy of FORD MOTOR CO.
    • Are the voltages greater than 2.5 volts and less than 3.0 volts while flexing the wire harness? 

    Yes  : GO to  BK4.

    No  : REPAIR circuit 4-EC7 (GY/RD) or circuit 5-EC7 (BU/RD) as necessary. If a wiring fault is not found and repaired, REFER to MODULE COMMUNICATIONS NETWORK for additional diagnostics of the HS-CAN. GO to  BK6.

  4. BK4 CHECK THE HS-CAN CIRCUITS BETWEEN THE RCM AND DLC C251 FOR AN OPEN 
    • Key in OFF position.
    • Depower the system. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING  in this article.
    • While monitoring the meter, attempt to recreate the hard fault by flexing the wire harness and measure the resistance between RCM C2041b-19, circuit 4-EC18 (GY/BK), harness side and DLC C2551-6, circuit 4-EC7 (GY/RD), harness side; and between RCM C2041b-20, circuit 5-EC18 (BU/BK), harness side and DLC C251-14, circuit 5-EC7 (BU/RD), harness side.
      Fig 3: Checking HS-CAN Circuits Between RCM And DLC C251 For Open
      G04654978Courtesy of FORD MOTOR CO.
    • Are the resistances less than 0.5 ohm while flexing the wire harness? 

    Yes  : GO to  BK5.

    No  : REPAIR circuit 4-EC18 (GY/BK), 4-EC7 (GY/RD), 5-EC18 (BU/BK) or circuit 5-EC7 (BU/RD). GO to  BK6.

  5. BK5 CHECK THE HS-CAN NETWORK 
    NOTE: Make sure the safety belt pretensioner restraint system diagnostic tools, sensor electrical connectors, and the RCM electrical connectors are connected before carrying out the on-demand self test. If not, erroneous DTCs will be recorded.
    • Connect: RCM C2041a and C2041b.
    • Repower the system. Do not  prove out the system at this time. Refer to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING  in this article.
    • Enter the following diagnostic mode on the scan tool: Carry Out The Data Link Diagnostics.
    • Did the Data Link Diagnostics test pass? 

    Yes  : The condition that caused the fault can not be found at this time. GO to  BK6.

    No  : REFER to MODULE COMMUNICATIONS NETWORK . GO to BK6.

  6. BK6 CHECK FOR ADDITIONAL DTCs 
    • Refer to the continuous DTCs recorded during Step BK1.
    • Were any continuous DTCs retrieved during Step BK1? 

    Yes  : Do not clear any DTCs until all DTCs have been resolved. GO to the DIAGNOSTIC TROUBLE CODES (DTCS)  in this article for pinpoint test direction.

    No  : RECONNECT the system. If previously directed to deactivate the system, REACTIVATE the system. REFER to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEACTIVATION AND REACTIVATION  in this article. REPOWER the system. REFER to SUPPLEMENTAL RESTRAINT SYSTEM (SRS) DEPOWERING AND REPOWERING  in this article. PROVE OUT the system. CLEAR all DTCs.

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