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Pinpoint Test D: The Subwoofer Is Inoperative

WARNING: This page is about a different car, the 2010 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Audio System for schematic and connector information.

Normal Operation 

The subwoofer amplifier receives voltage through circuit 720 (RD/YE) and ground through circuit 694 (BK/LG). Audio signals are sent to the subwoofer amplifier from the audio unit through circuits 167 (BN/OG) and 168 (RD/BK). The enable/clip circuit 173 (DG/VT) carries out 2 functions: to turn the subwoofer amplifier on, and to monitor an overload condition to the subwoofer amplifier. In the event of an overload, the audio unit clips the audio output signal to the subwoofer amplifier (heard as distortion).

This pinpoint test is intended to diagnose the following:

PINPOINT TEST D: THE SUBWOOFER IS INOPERATIVE 

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. D1 CHECK CIRCUIT 720 (RD/YE) FOR VOLTAGE 
    • Key in OFF position.
    • Disconnect: Subwoofer Amplifier C466
      • Fig 1: Checking Circuit For Voltage
      GF0018996Courtesy of FORD MOTOR CO.
    • Measure the voltage between the subwoofer amplifier C466-5, circuit 720 (RD/YE), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  D2.
    2. NO  : VERIFY the battery junction box (BJB) fuse 12 (20A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation. If not OK, REFER to appropriate SYSTEM WIRING DIAGRAMS article to identify the possible causes of the circuit short.
  2. D2 CHECK CIRCUIT 694 (BK/LG) FOR AN OPEN 
      Fig 2: Checking Circuit For Open
      GF0018997Courtesy of FORD MOTOR CO.
    • Measure the resistance between the subwoofer amplifier C466-3, circuit 694 (BK/LG), harness side and ground.
    • Is the resistance less than 5 ohms? 
    1. YES  : Go to  D3.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
  3. D3 CHECK CIRCUIT 173 (DG/VT) FOR VOLTAGE 
    • Key in ON position.
    • Operate the audio system in radio tuner (AM/FM) mode.
      • Fig 3: Checking Circuit For Voltage
      GF0001364Courtesy of FORD MOTOR CO.
    • Measure the voltage between the subwoofer amplifier C466-1, circuit 173 (DG/VT), harness side and ground.
    • Is the voltage between 3.8 and 6.7 volts? 
    1. YES  : Go to  D6.
    2. NO  : Go to  D4.
  4. D4 CHECK CIRCUIT 173 (DG/VT) FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Audio Unit C290b
    • Key in ON position.
      • Fig 4: Checking Circuit For Voltage
      GF0001364Courtesy of FORD MOTOR CO.
    • Measure the voltage between the subwoofer amplifier C466-1, circuit 173 (DG/VT), harness side and ground.
    • Is any voltage present? 
    1. YES  : REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
    2. NO  : Go to  D5.
  5. D5 CHECK CIRCUIT 173 (DG/VT) FOR AN OPEN OR SHORT TO GROUND 
    • Key in OFF position.
      • Fig 5: Checking Circuit For Open Or Short To Ground
      GF0004541Courtesy of FORD MOTOR CO.
    • Measure the resistance between the subwoofer amplifier C466-1, circuit 173 (DG/VT), harness side and the audio unit C290b-4, circuit 173 (DG/VT), harness side; and between the subwoofer amplifier C466-1, circuit 173 (DG/VT), harness side and ground.
    • Is the resistance less than 5 ohms between the subwoofer amplifier and the audio unit, and greater than 10,000 ohms between the subwoofer amplifier and ground? 
    1. YES  : INSTALL a new audio unit. REFER to Audio Unit . TEST the system for normal operation.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation.
  6. D6 CHECK THE AUDIO SIGNAL TO THE SUBWOOFER AMPLIFIER 
    • Operate the audio unit in radio tuner (AM/FM) mode.
      • Fig 6: Checking Audio Signal
      GF0004542Courtesy of FORD MOTOR CO.
    • Measure the AC voltage between the subwoofer amplifier C466-7, circuit 167 (BN/OG), harness side and the subwoofer amplifier C466-8, circuit 168 (RD/BK), harness side.
    • Is a fluctuating AC voltage present? 
    1. YES  : INSTALL a new subwoofer amplifier. REFER to Subwoofer Amplifier . CLEAR the DTCs. TEST the system for normal operation.
    2. NO  : Go to  D7.
  7. D7 CHECK THE SUBWOOFER AUDIO CIRCUITS FOR A SHORT TO VOLTAGE 
    • Key in OFF position.
    • Disconnect: Audio Unit C290b
    • Key in ON position.
      • Fig 7: Checking Circuits For Short To Voltage
      GF0018998Courtesy of FORD MOTOR CO.
    • Measure the voltage between the subwoofer amplifier C466-7, circuit 167 (BN/OG), harness side and ground; and between the subwoofer amplifier C466-8, circuit 168 (RD/BK), harness side and ground.
    • Is any voltage present? 
    1. YES  : REPAIR the circuit in question. CLEAR the DTCs. TEST the system for normal operation.
    2. NO  : Go to  D8.
  8. D8 CHECK THE SUBWOOFER AUDIO CIRCUITS FOR AN OPEN OR SHORT TO GROUND 
    • Key in OFF position.
    • Measure the resistance between the subwoofer amplifier, harness side and the audio unit, harness side; and between the subwoofer amplifier, harness side and ground as follows:
      Subwoofer Amplifier Connector-Pin Audio Unit Connector-Pin Circuit
      C466-7 C290b-1 167 (BN/OG)
      C466-8 C290b-2 168 (RD/BK)
    • Is the resistance less than 5 ohms between the subwoofer amplifier and the audio unit, and greater than 10,000 ohms between the subwoofer amplifier and ground? 
    1. YES  : INSTALL a new audio unit. REFER to Audio Unit . TEST the system for normal operation.
    2. NO  : REPAIR the circuit. CLEAR the DTCs. TEST the system for normal operation after the repair.
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