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Home >> Mercury >> 2008 >> Milan Base, 3.0 1, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 734 (Supplemental Inflatable Restraint System - F-150 & Mark LT) >> Diagnostic Tests >> Pinpoint Tests - Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) >> Pinpoint Tests >> Pinpoint Test S: LFC 16/DTC B2909 - Belt Tension Sensor Fault >> Pinpoint Test S: LFC 16/DTC B2909 - Belt Tension Sensor Fault

Pinpoint Test S: LFC 16/DTC B2909 - Belt Tension Sensor Fault

WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Connector C3238 is located at the anchor point of the safety belt. On vehicles equipped with seat integrated restraints (SIR), the belt tension sensor is located on the outboard side of the passenger seat. On vehicles equipped without SIR, the belt tension sensor is located near the base of the B-pillar.
NOTE: To identify between a production OCS system and an OCS system service kit (OCS service kit), inspect the OCS ECU electrical connector.  

A production OCS system allows the disconnect of the electrical connector from the OCS ECU.

An OCS system service kit has the OCS ECU electrical connector glued to the ECU. It cannot and should not be disconnected or altered.

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. S1 CHECK FOR CONTINUOUS OR ON-DEMAND SELF TEST 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 diagnostic tool: On-Demand Self Test/Retrieve and Record Continuous Memory DTCs
    • Enter the following diagnostic mode on the diagnostic tool: View and Record DTC B2909 Fault PIDs
    • Was on-demand DTC B2909 retrieved? 
    1. YES  : This is a hard fault. The fault condition is still present. This fault cannot be cleared until it is corrected and the DTC is no longer retrieved during the on-demand self test.

      Using the fault PIDs recorded, go to the appropriate pinpoint test step.

      Vehicles with a production OCS system 

      For belt tension sensor with a circuit fault, go to  S2 .

      For belt tension sensor with a short to ground fault, go to  S4 .

      Vehicles with a service OCS system 

      For belt tension sensor with a circuit fault, go to  S8 .

      For belt tension sensor with a short to ground fault, go to  S10 .

    2. NO  : This is an intermittent fault when present as a continuous memory DTC only (DTC not retrieved on-demand). The fault condition is not present at this time. Go to  S16 .
  2. S2 CHECK THE BELT TENSION SENSOR CIRCUITS FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Disconnect: Passenger Safety Belt Buckle Pretensioner C3202 (Vehicles with Seat Integrated Restraints (SIR) only)
    • Connect: Restraint System Diagnostic Tool 418-F395 to Passenger Safety Belt Buckle Pretensioner C3202 (Vehicles with SIR only)
    • Disconnect: Belt Tension Sensor C3238
    • Disconnect: OCS ECU C3043
    • 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.
    • Measure the voltage between OCS ECU C3043-11, circuit 2088 (TN/RD), harness side and ground; C3043-13, circuit 2090 (DB/OG), harness side and ground; C3043-12, circuit 2089 (OG/BK), harness side and ground.
      • Fig 1: Checking Belt Tension Sensor Circuits For Short To Voltage
      GF0002198Courtesy of FORD MOTOR CO.
    • Are the voltages less than 0.2 volt? 
    1. YES  : Go to  S3.
    2. NO  : REPAIR circuit 2088 (TN/RD), circuit 2089 (OG/BK) or circuit 2090 (DB/OG). Go to  S17 .
  3. S3 CHECK BELT TENSION SENSOR CIRCUITS FOR OPEN 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Measure the resistance between OCS C3043-11, circuit 2088 (TN/RD), harness side and the belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side; between OCS C3043-13, circuit 2090 (DB/OG), harness side and the belt tension sensor C3238-2, circuit 2090 (DB/OG), harness side; and between OCS C3043-12, circuit 2089 (OG/BK), harness side and belt tension sensor C3238-3, circuit 2089 (OG/BK), harness side.
      • Fig 2: Checking Belt Tension Sensor Circuits For Open
      GF0002199Courtesy of FORD MOTOR CO.
    • Are the resistances less than 0.5 ohm? 
    1. YES  : Go to  S5.
    2. NO  : REPAIR circuit 2088 (TN/RD), circuit 2089 (OG/BK) or circuit 2090 (DB/OG).

      Go to  S17.

  4. S4 CHECK CIRCUITS 2088 (TN/RD), 2089 (OG/BK) and 2090 (DB/OG) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Measure the resistance between OCS ECU C3043-11, circuit 2088 (TN/RD), harness side and ground; and between OCS ECU C3043-12, circuit 2089 (OG/BK) harness side and ground; and between OCS ECU C3043-13, circuit 2090 (DB/OG), harness side and ground.
      • Fig 3: Checking Circuits 2088 (TN/RD), 2089 (OG/BK) And 2090 (DB/OG) For Short To Ground
      GF0002200Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,0000 ohms? 
    1. YES  : Go to  S5.
    2. NO  : REPAIR circuit 2088 (TN/RD), circuit 2089 (OG/BK) or circuit 2090 (DB/OG). Go to  S17 .
  5. S5 CHECK CIRCUITS 2088 (TN/RD), 2089 (OG/BK) AND 2090 (DB/OG) FOR A SHORT 
    • Measure the resistance between OCS ECU:
      • C3043-11, circuit 2088 (TN/RD), harness side and C3043-12, circuit 2089 (OG/BK), harness side.
      • C3043-11, circuit 2088 (TN/RD), harness side and C3043-13, circuit 2090 (DB/OG), harness side.
      • C3043-12, circuit 2089 (OG/BK), harness side and C3043-13, circuit 2090 (DB/OG), harness side.
      • Fig 4: Checking Circuits 2088 (TN/RD), 2089 (OG/BK) And 2090 (DB/OG) For Short
      GF0002201Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,0000 ohms? 
    1. YES  : Go to  S6.
    2. NO  : REPAIR circuit 2088 (TN/RD), circuit 2090 (DB/OG) or circuit 2089 (OG/BK). Go to  S17 .
  6. S6 CHECK OCS ECU OUTPUT 
    • Connect: OCS ECU C3043
    • 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.
    • Measure the voltage between belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side and C3238-2, circuit 2090 (DB/OG), harness side.
      • Fig 5: Checking OCS ECU Output
      GF0002202Courtesy of FORD MOTOR CO.
    • Is the voltage approximately 5 volts? 
    1. YES  : Go to  S7.
    2. NO  : INSTALL a new OCS system service kit. REFER to Occupant Classification Sensor  in this article. Go to  S17 .
  7. S7 CHECK BELT TENSION SENSOR VOLTAGE OUTPUT 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Connect a fused jumper lead between belt tension sensor C3238 pin 1, circuit 2088 (TN/RD), harness side and pin 1, circuit 2088 (TN/RD), component side.
    • Connect a fused jumper lead between belt tension sensor C3238 pin 2, circuit 2090 (DB/OG), harness side and pin 2, circuit 2090 (DB/OG), component side.
    • 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.
    • Measure the voltage between belt tension sensor C3238 pin 3, circuit 2089 (OG/BK), component side and ground as you vary the tension of the belt tension sensor.
      • Fig 6: Checking Belt Tension Sensor Voltage Output
      GF0002203Courtesy of FORD MOTOR CO.
    • Does the voltage vary from approximately 0.95 volt with no tension applied to the sensor to approximately 3.8 volts with full tension applied to the sensor? 
    1. YES  : Go to  S14.
    2. NO  : INSTALL a new belt tension sensor. REFER to SAFETY BELT SYSTEM article. Go to  S17 .
  8. S8 CHECK THE BELT TENSION SENSOR CIRCUITS FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Disconnect: Passenger Safety Belt Buckle Pretensioner C3202 (Vehicles with Seat Integrated Restraints (SIR) only)
    • Connect: Restraint System Diagnostic Tool 418-F395 to Passenger Safety Belt Buckle Pretensioner C3202 (Vehicles with SIR only)
    • Disconnect: Belt Tension Sensor C3238
    • 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.
    • Measure the voltage between belt tension sensor C3238-3, circuit 2089 (OG/BK), harness side and ground; and between belt tension sensor C3238-2, circuit 2090 (DB/OG), harness side and ground; and between belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side and ground.
      • Fig 7: Checking Belt Tension Sensor Circuits For Short To Voltage
      GF0002204Courtesy of FORD MOTOR CO.
    • Are the voltages less than 0.2 volt for C3238-2 and C3238-3 and approximately 5 volts for C3238-1? 
    1. YES  : For vehicles with SIR seats,  Go to  S9 .

      For vehicles without SIR seats,  Go to  S10 .

    2. NO  : REPAIR circuit 2089 (OG/BK), circuit 2090 (DB/OG) or circuit 2088 (TN/RD). Go to  S17 .
  9. S9 CHECK THE BELT TENSION SENSOR CIRCUITS FOR AN OPEN 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Disconnect: Belt Tension Sensor C3238
    • Disconnect: Passenger Seat C300
    • Measure the resistance between belt tension sensor C3238-3, circuit 2089 (OG/BK), harness side and passenger seat C300-3, circuit 2089 (OG/BK), harness side; and between belt tension sensor C3238-2, circuit 2090 (DB/OG), harness side and passenger seat C300-2, circuit 2090 (DB/OG), harness side; and between belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side and passenger seat C300-1, circuit 2088 (TN/RD), harness side.
      • Fig 8: Checking Belt Tension Sensor Circuits For An Open
      GF0002205Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  S12.
    2. NO  : REPAIR circuit 2089 (OG/BK), circuit 2090 (DB/OG) or circuit 2088 (TN/RD). Go to  S17 .
  10. S10 CHECK THE BELT TENSION SENSOR CIRCUITS 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Carry out a thorough visual inspection of the OCS system wiring, terminals and connectors, the belt tension sensor wiring, terminals and connectors and the related seat wiring harness and body wiring harness terminals and connectors.
    • Were any problems noted? 
    1. YES  : REPAIR the seat connectors and wiring as needed. Go to  S17 .
    2. NO  : Go to  S12.
  11. S11 CHECK THE BELT TENSION SENSOR 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.
    • Disconnect: Belt Tension Sensor C3238
    • Measure the resistance between belt tension sensor C3238-3, circuit 2089 (OG/BK), harness side and ground, and between belt tension sensor C3238-2, circuit 2090 (DB/OG), harness side and ground, and between belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side and ground.
      • Fig 9: Checking Belt Tension Sensor Circuits For Short To Ground
      GF0002206Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms for C3238-1 and C3238-3 and less than 5 ohms for C3238-2? 
    1. YES  : Go to  S12.
    2. NO  : REPAIR circuit 2089 (OG/BK), circuit 2090 (DB/OG) or circuit 2088 (TN/RD). Go to  S17 .
  12. S12 CHECK CIRCUITS 2088 (TN/RD), 2089 (OG/BK) AND 2090 (DB/OG) FOR A SHORT 
    • Measure the resistance between belt tension sensor:
      • C3238-1, circuit 2088 (TN/RD), harness side and C3238-3, circuit 2089 (OG/BK), harness side.
      • C3238-1, circuit 2088 (TN/RD), harness side and C3238-2, circuit 2090 (DB/OG), harness side.
      • C3238-3, circuit 2089 (OG/BK), harness side and C3238-2, circuit 2090 (DB/OG), harness side.
      • Fig 10: Checking Circuits 2088 (TN/RD), 2089 (OG/BK) And 2090 (DB/OG) For Short
      GF0002207Courtesy of FORD MOTOR CO.
    • Are the resistances greater than 10,000 ohms? 
    1. YES  : Go to  S13.
    2. NO  : REPAIR circuit 2088 (TN/RD), circuit 2090 (DB/OG) or circuit 2089 (OG/BK). Go to  S17 .
  13. S13 CHECK OCS ECU OUTPUT 
    • 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.
    • Measure the voltage between belt tension sensor C3238-1, circuit 2088 (TN/RD), harness side and C3238-2, circuit 2090 (DB/OG), harness side.
      • Fig 11: Checking OCS ECU Output
      GF0002202Courtesy of FORD MOTOR CO.
    • Is the voltage approximately 5 volts? 
    1. YES  : Go to  S14.
    2. NO  : INSTALL a new OCS system service kit. REFER to Occupant Classification Sensor  in this article. Go to  S17 .
  14. S14 CHECK BELT TENSION SENSOR VOLTAGE OUTPUT 
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Connect a fused jumper lead between belt tension sensor C3238 pin 1, circuit 2088 (TN/RD), harness side and pin 1, circuit 2088 (TN/RD), component side.
    • Connect a fused jumper lead between belt tension sensor C3238 pin 2, circuit 2090 (DB/OG), harness side and pin 2, circuit 2090 (DB/OG), component side.
    • 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.
    • Measure the voltage between belt tension sensor C3238 pin 3, circuit 2089 (OG/BK), component side and ground as you vary the tension of the belt tension sensor.
      • Fig 12: Checking Belt Tension Sensor Voltage Output
      GF0002203Courtesy of FORD MOTOR CO.
    • Does the voltage vary from approximately 0.95 volt with no tension applied to the sensor to approximately 3.8 volts with full tension applied to the sensor? 
    1. YES  : Go to  S15.
    2. NO  : INSTALL a new belt tension sensor. REFER to SAFETY BELT SYSTEM article. Go to  S17 .
  15. S15 CONFIRM THE BELT TENSION SENSOR FAULT 
    NOTE: Make sure all restraint system diagnostic tools, sensor electrical connectors and the RCM electrical connector are connected before carrying out the on-demand self test. If not, erroneous DTCs will be recorded.
    • Key in OFF position.
    • Depower the system. Refer to Supplemental Restraint System (SRS) Depowering and Repowering  in this article.
    • Connect: OCS ECU (if disconnected previously)
    • Connect: Belt Tension Sensor C3238
    • Connect: Passenger Seat C300 (vehicles without SIR seats) (if disconnected previously)
    • 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 diagnostic tool: On-Demand Self Test/Retrieve and Record Continuous Memory DTCs
    • Enter the following diagnostic mode on the diagnostic tool: View and Record DTC B2909 Fault PIDs
    • Was on-demand DTC B2909 retrieved? 
    1. YES  : INSTALL a new OCS system service kit. REFER to Occupant Classification Sensor  in this article. Go to  S17 .
    2. NO  : CHECK for causes of the intermittent fault. ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently. ACTIVATE other systems in the same wire harness. REPAIR any intermittent concerns found. Go to  S17 .
  16. S16 CHECK FOR AN INTERMITTENT FAULT 
    • Key in OFF position.
    • Enter the following diagnostic mode on the diagnostic tool: On-Demand Self Test/Retrieve and Record Continuous Memory DTCs
    • Enter the following diagnostic mode on the diagnostic tool: View and Record DTC B2909 Fault PIDs
    • Was on-demand DTC B2909 retrieved? 
    1. YES  : This is a hard fault. The fault condition is now present. This fault cannot be cleared until it is corrected and the DTC is no longer retrieved during the on-demand self test.

      Using the fault PIDs recorded, go to the appropriate pinpoint test step.

      Vehicles with a production OCS system 

      For belt tension sensor with a circuit fault, go to  S2 .

      For belt tension sensor with a short to ground fault, go to  S4 .

      Vehicles with a service OCS system 

      For belt tension sensor with a circuit fault, go to  S8 .

      For belt tension sensor with a short to ground fault, go to  S11 .

    2. NO  : CHECK for causes of the intermittent fault. ATTEMPT to recreate the hard fault by flexing the wire harness and cycling the ignition key frequently. ACTIVATE other systems in the same wire harness. REPAIR any intermittent concerns found. Go to  S17 .
  17. S17 CHECK FOR ADDITIONAL DTCs 
    • Refer to the continuous memory DTCs recorded during Step S1.
    • Were any continuous memory DTCs retrieved during Step S1? 
    1. YES  : Do not clear any DTCs until all DTCs have been resolved. Go to the Restraints Control Module (RCM) Diagnostic Trouble Code (DTC) Table in this article for pinpoint test direction.
    2. 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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