Pinpoint Test D: The Subwoofer Is Inoperative

WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: On vehicles equipped with a CD6 audio unit, interrupting battery power within 30 seconds of repowering will damage the audio unit. To prevent audio unit damage, do not disconnect the battery (or audio unit), reconnect the battery (or audio unit), and then disconnect it again within 30 seconds.

D1 CHECK CIRCUIT 174 (GY/BK) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Subwoofer Amplifier C466.
- Key in ON position.
- Turn the audio unit on.
- Measure the voltage between the subwoofer amplifier C466-1, circuit 174 (GY/BK), harness side and ground.
  
  Fig 1: Checking Circuit 174 (GY/BK) For Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 4.1 volts?
Yes : GO to D2.

No : GO to D6.
D2 CHECK CIRCUIT 720 (RD/YE) FOR VOLTAGE
- Key in OFF position.
- Measure the voltage between the subwoofer amplifier C466-5, circuit 720 (RD/YE), harness side and ground.
  
  Fig 2: Checking Circuit 720 (RD/YE) For Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to D3.

No : VERIFY the smart junction box (SJB) fuse 16 (15A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
D3 CHECK CIRCUIT 694 (BK/LG) FOR AN OPEN
- Measure the resistance between the subwoofer amplifier C466-2, circuit 694 (BK/LG), harness side and ground.
  
  Fig 3: Checking Circuit 694 (BK/LG) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : GO to D4.

No : REPAIR the circuit. TEST the system for normal operation.
D4 CHECK FOR AN OUTPUT SIGNAL FROM THE AUDIO UNIT
- Key in ON position.
- Turn the audio unit on.
- Measure the AC voltage between the subwoofer amplifier C466-7, circuit 169 (LG/BK), harness side and the subwoofer amplifier C466-8, circuit 172 (LB/RD), harness side.
  
  Fig 4: Checking An Output Signal From Audio Unit
  Courtesy of FORD MOTOR CO.
- Is there a fluctuating AC voltage?
Yes : REMOVE the subwoofer amplifier. REFER to SUBWOOFER AMPLIFIER in this article. SEND it to an authorized audio system repair facility. TEST the system for normal operation after the repair.

No : GO to D5.

D5 CHECK CIRCUITS 172 (LB/RD) AND 169 (LG/BK) FOR AN OPEN OR A SHORT TO GROUND

Key in OFF position.
Disconnect: Audio Unit C290b.

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 REFERENCE

Subwoofer Amplifier Connector-Pin	Audio Unit Connector-Pin or Ground	Circuit
C466-7	C240b-1	169 (LG/BK)
C466-7	Ground	169 (LG/BK)
C466-8	C240b-2	172 (LB/RD)
C466-8	Ground	172 (LB/RD)

Measure the resistance between the subwoofer amplifier C466-7, circuit 169 (LG/BK), harness side and the audio unit C240b-1, circuit 169 (LG/BK), harness side; and between the subwoofer amplifier C466-7, circuit 169 (LG/BK), harness side and ground. Measure the resistance between the subwoofer amplifier C466-8, circuit 172 (LB/RD), harness side and the audio unit C240b-2, circuit 172 (LB/RD), harness side; and between the subwoofer amplifier C466-8, circuit 172 (LB/RD), 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?

Yes : SEND the audio unit to an authorized audio system repair facility. TEST the system for normal operation after the repair.

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

D6 CHECK CIRCUIT 174 (GY/BK) FOR AN OPEN OR A SHORT TO GROUND
- Key in OFF position.
- Disconnect: Audio Unit C240b.
- Measure the resistance between the subwoofer amplifier C466-1, circuit 174 (GY/BK), harness side and the audio unit C240b-4, circuit 174 (GY/BK), harness side; and between the subwoofer amplifier C466-1, circuit 174 (GY/BK), harness side and ground.
  
  Fig 5: Checking Circuit 174 (GY/BK) For An Open Or A Short To Ground
  Courtesy of FORD MOTOR CO.
- Is the resistances less than 5 ohms between the connectors, and greater than 10,000 ohms between the subwoofer amplifier and ground?
Yes : SEND the audio unit to an authorized audio system repair facility. TEST the system for normal operation after the repair.

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