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Pinpoint Test N: The Passenger Heated Seat Is Inoperative

WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
  1. N1 CHECK VOLTAGE TO THE HEATED SEAT MODULE 
    WARNING: The restraint system diagnostic tool is for restraint system service only. Remove from vehicle prior to road use. Failure to remove could result in injury and possible violation of vehicle safety standards.
    NOTE:
    1. If a seat equipped with a supplemental restraint system (SRS) component is being serviced, the SRS must be depowered.  Refer to DEPOWERING PROCEDURE .
    2. The air bag warning lamp illuminates when the RCM fuse is removed and the ignition switch is ON. This is normal operation and does not indicate a supplemental restraint system (SRS) fault.
    3. The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
    • Key in OFF position.
      • WARNING: Be sure that nobody is in the vehicle and that there is nothing blocking or set in front of any air bag module when the battery ground cable is connected.
    • For vehicles equipped with seat side air bags, carry out the following:
      • Depower the SRS. REFER to DEPOWERING PROCEDURE .
      • Disconnect passenger seat side air bag C3227.
      • Connect restraint system diagnostic tool 418-133 to passenger seat side air bag C3227.
      • Connect the battery ground cable.
    • Disconnect: Passenger Heated Seat Module C329.
    • Key in ON position.
    • Measure the voltage between passenger heated seat module C329-12, circuit 1048 (LB/WH), harness side and ground; and between passenger heated seat module C329-5, circuit 972 (BK/WH), harness side and ground.
      Fig 1: Checking Voltage To Heated Seat Module
      G04658679Courtesy of FORD MOTOR CO.
    • Are the voltages greater than 10 volts? 

    Yes:  GO to  N2.

    No:  VERIFY battery junction box (BJB) fuse 22 (30A) and smart junction box (SJB) fuse 19 (10A) are OK. If OK, REPAIR the affected circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  2. N2 CHECK THE HEATED SEAT MODULE GROUND 
    • Key in OFF position.
    • Measure the resistance between passenger heated seat module C329-1, circuit 1205 (BK), harness side and ground.
      Fig 2: Checking Heated Seat Module Ground
      G04658680Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 

    Yes:  GO to  N3.

    No:  REPAIR circuit 1205 (BK). TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  3. N3 CHECK THE HEATED SEAT TEMPERATURE SENSOR CIRCUITS FOR A SHORT TO VOLTAGE 
    • Key in ON position.
    • Measure the voltage between passenger heated seat module C329-3, circuit 2121 (BN/LB), harness side and ground; and between C329-4, circuit 2120 (BK/LB), harness side and ground.
      Fig 3: Checking Heated Seat Temperature Sensor Circuits For Short To Voltage
      G04658681Courtesy of FORD MOTOR CO.
    • Is voltage present on either circuit? 

    Yes:  REPAIR the affected circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  GO to  N4.

  4. N4 CHECK THE HEATED SEAT TEMPERATURE SENSOR 
    • Key in OFF position.
    • Measure the resistance between passenger heated seat module C329-3, circuit 2121 (BN/LB), harness side and C329-4, circuit 2120 (BK/LB), harness side; and between C329-3, circuit 2121 (BN/LB), harness side and ground.
      Fig 4: Checking Heated Seat Temperature Sensor
      G04658682Courtesy of FORD MOTOR CO.
    • Is the resistance between 50 ohms and 300,000 ohms between C329-3 and C329-4, and greater than 10,000 ohms between C329-3 and ground? 

    Yes:  GO to  N7.

    No:  GO to  N5.

  5. N5 CHECK CIRCUIT 2120 (BK/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Disconnect: Passenger Seat Cushion Heated Seat Element C334.
    • Measure the resistance between passenger heated seat module C329-4, circuit 2120 (BK/LB), harness side and passenger seat cushion heated seat element C334-2, circuit 2120 (BK/LB), harness side; and between passenger heated seat module C329-4, circuit 2120 (BK/LB), harness side and ground.
      Fig 5: Checking Circuit 2120 (BK/LB) For Open Or Short To Ground
      G04658683Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between C329-4 and C334-2, and greater than 10,000 ohms between C329-4 and ground? 

    Yes:  GO to  N6.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  6. N6 CHECK CIRCUIT 2121 (BN/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Measure the resistance between passenger heated seat module C329-3, circuit 2121 (BN/LB), harness side and passenger seat cushion heated seat element C334-3, circuit 2121 (BN/LB), harness side; and between passenger heated seat module C329-3, circuit 2121 (BN/LB), harness side and ground.
      Fig 6: Checking Circuit 2121 (BN/LB) For Open Or Short To Ground
      G04658684Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between C329-3 and C334-3, and greater than 10,000 ohms between C329-3 and ground? 

    Yes:  INSTALL a new passenger seat cushion heated seat element. REFER to SEAT CUSHION - PASSENGER . REFER to OCCUPANT CLASSIFICATION SENSOR - SERVICE KIT . TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  7. N7 CHECK THE SEAT CUSHION HEATED SEAT ELEMENT AND THE SEAT BACK HEATED SEAT ELEMENT FOR A SHORT TO VOLTAGE 
    • Key in ON position.
    • Measure the voltage between passenger heated seat module C329-6, circuit 2124 (YE/LB), harness side and ground; and between C329-7, circuit 2127 (VT/LB), harness side and ground.
      Fig 7: Checking Seat Cushion Heated Seat Element & Seat Back Heated Seat Element For Short To Voltage
      G04658685Courtesy of FORD MOTOR CO.
    • Is voltage present on either circuit? 

    Yes:  REPAIR circuit 2124 (YE/LB), circuit 2127 (VT/LB) or circuit 2126 (GY/LB). TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  GO to  M8.

  8. N8 CHECK THE SEAT CUSHION HEATED SEAT ELEMENT AND SEAT BACK HEATED SEAT ELEMENT CIRCUITS 
    • Key in OFF position.
    • Measure the resistance between passenger heated seat module C329-6, circuit 2124 (YE/LB), harness side and C329-7, circuit 2127 (VT/LB), harness side; and between passenger heated seat module C329-6, circuit 2124 (YE/LB), harness side and ground
      Fig 8: Checking Seat Cushion Heated Seat Element & Seat Back Heated Seat Element Circuits
      G04658686Courtesy of FORD MOTOR CO.
    • Is the resistance between 1.6 ohms and 10 ohms between C329-6 and C329-7, and greater than 10,000 ohms between C329-6 and ground? 

    Yes:  GO to  N13.

    No:  GO to  N9.

  9. N9 CHECK CIRCUIT 2124 (YE/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Disconnect: Passenger Seat Cushion Heated Seat Element C334.
    • Measure the resistance between passenger heated seat module C329-6, circuit 2124 (YE/LB), harness side and passenger seat cushion heated seat element C334-1, circuit 2124 (YE/LB), harness side; and between passenger heated seat module C329-6, circuit 2124 (YE/LB), harness side and ground.
      Fig 9: Checking Circuit 2124 (YE/LB) For Open Or Short To Ground
      G04658687Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between C329-6 and C334-1, and greater than 10,000 ohms between C329-6 and ground? 

    Yes:  GO to  N10.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  10. N10 CHECK CIRCUIT 2127 (VT/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Disconnect: Passenger Seat Backrest Heated Seat Element C335.
    • Measure the resistance between passenger heated seat module C329-7, circuit 2127 (VT/LB), harness side and passenger seat backrest heated seat element C335-1, circuit 2127 (VT/LB), harness side; and between passenger heated seat module C329-7, circuit 2127 (VT/LB), harness side and ground.
      Fig 10: Checking Circuit 2127 (VT/LB) For Open Or Short To Ground
      G04658688Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between C329-7 and C335-1, and greater than 10,000 ohms between C329-7 and ground? 

    Yes:  GO to  N11.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  11. N11 CHECK CIRCUIT 2126 (GY/LB) FOR AN OPEN OR SHORT TO GROUND 
    • Measure the resistance between passenger seat cushion heated seat element C334-4, circuit 2126 (GY/LB), harness side and passenger seat backrest heated seat element C335-2, circuit 2126 (GY/LB), harness side; and between passenger seat cushion heated seat element C334-4, circuit 2126 (GY/LB), harness side and ground.
      Fig 11: Checking Circuit 2126 (GY/LB) For Open Or Short To Ground
      G04658689Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms between C334-4 and C335-2, and greater than 10,000 ohms between C334-4 and ground? 

    Yes:  GO to  N12.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  12. N12 CHECK THE PASSENGER SEAT BACKREST HEATED SEAT ELEMENT 
    • Measure the resistance between passenger seat backrest heated seat element C335 pin 1, component side and C335 pin 2, component side.
      Fig 12: Checking Passenger Seat Backrest Heated Seat Element
      G04658690Courtesy of FORD MOTOR CO.
    • Is the resistance between 0.6 and 1.2 ohms? 

    Yes:  INSTALL a new passenger seat cushion heated seat element. REFER to SEAT CUSHION - PASSENGER . REFER to OCCUPANT CLASSIFICATION SENSOR - SERVICE KIT . TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  INSTALL a new passenger seat backrest heated seat element. REFER to SEAT BACKREST - FRONT . TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  13. N13 CHECK CIRCUIT 1256 (WH/YE) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: EATC Module C228b.
    • Key in ON position.
    • Measure the voltage between passenger heated seat module C329-8, circuit 1256 (WH/YE), harness side and ground.
      Fig 13: Checking Circuit 1256 (WH/YE) For Short To Voltage
      G04658691Courtesy of FORD MOTOR CO.
    • Is the voltage less than 0.2 volt? 

    Yes:  GO to  N14.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  14. N14 CHECK CIRCUIT 1256 (WH/YE) FOR A SHORT TO GROUND 
    • Key in OFF position.
    • Measure the resistance between passenger heated seat module C329-8, circuit 1256 (WH/YE), harness side and ground.
      Fig 14: Checking Circuit 1256 (WH/YE) For Short To Ground
      G04658692Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 

    Yes:  GO to  N15.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  15. N15 CHECK CIRCUIT 1256 (WH/YE) FOR AN OPEN 
    • Measure the resistance between passenger heated seat module C329-8, circuit 1256 (WH/YE), harness side and EATC module C228b-19, circuit 1256 (WH/YE), harness side.
      Fig 15: Checking Circuit 1256 (WH/YE) For Open
      G04658693Courtesy of FORD MOTOR CO.
    • Is the resistance less than 5 ohms? 

    Yes:  GO to  N16.

    No:  REPAIR the circuit. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  16. N16 CHECK THE HEATED SEAT MODULE 
    • Connect: Passenger Heated Seat Module C329.
    • Key in ON position.
    • Measure the voltage between EATC module C228b-20, circuit 2070 (GY/LB), harness side and ground; and between EATC module C228b-21, circuit 2069 (VT/LG), harness side and ground.
      Fig 16: Checking Heated Seat Module
      G04658694Courtesy of FORD MOTOR CO.
    • Are the voltages less than 0.2 volt? 

    Yes:  GO to  N18.

    No:  GO to  N17.

  17. N17 CHECK CIRCUITS 2070 (GY/LB) AND 2069 (VT/LG) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Passenger Heated Seat Module C329.
    • Key in ON position.
    • Measure the voltage between EATC module C228b-20, circuit 2070 (GY/LB), harness side and ground; and between EATC module C228b-21, circuit 2069 (VT/LG), harness side and ground.
      Fig 17: Checking Circuits 2070 (GY/LB) & 2069 (VT/LG) For Short To Voltage
      G04658695Courtesy of FORD MOTOR CO.
    • Are the voltages less than 0.2 volt? 

    Yes:  INSTALL a new heated seat module. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  REPAIR the affected circuits. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  18. N18 CHECK CIRCUITS 2070 (GY/LB) AND 2069 (VT/LG) FOR A SHORT 
    • Key in OFF position.
    • Measure the resistance between EATC module C228b-20, circuit 2070 (GY/LB), harness side and C228b-21, circuit 2069 (VT/LG), harness side.
      Fig 18: Checking Circuits 2070 (GY/LB) & 2069 (VT/LG) For Short
      G04658696Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 10,000 ohms? 

    Yes:  GO to  N19.

    No:  REPAIR the shorted circuits. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

  19. N19 CHECK THE EATC MODULE OUTPUT 
    • Connect: EATC Module C228b.
    • Connect: Passenger Heated Seat Module C329.
    • Key in ON position.
      • NOTE: The following measurement must be taken by back-probing the driver heated seat module C329.
      NOTE: The voltage on circuit 1256 (WH/YE) should drop momentarily when the driver heated seat control button is pressed.
      Fig 19: Checking EATC Module Output
      G04658697Courtesy of FORD MOTOR CO.
    • Measure the voltage between passenger heated seat module C329-8, circuit 1256 (WH/YE), harness side and ground by back-probing the passenger heated seat module C329-8. Press the passenger heated seat control button on the EATC module and note the voltage.
    • Is the voltage greater than 10 volts before pressing the driver heated seat control button, then momentarily drops when the heated seat control button is pressed? 

    Yes:  INSTALL a new passenger heated seat module. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    No:  If the voltage is greater than 10 volts but did not drop when the driver heated seat button was pressed, INSTALL a new EATC module. REFER to EATC MODULE . TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

    If the voltage is less than 10 volts, INSTALL a new driver heated seat module. TEST the system for normal operation.

    For vehicles equipped with seat side air bags, DISCONNECT the battery ground cable. DISCONNECT the restraint system diagnostic tool from passenger seat side air bag module C3227. CONNECT passenger seat side air bag module C3227. REPOWER the SRS. REFER to REPOWERING PROCEDURE .

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