Pinpoint Test D: The Subwoofer Is Inoperative/Does Not Operate Correctly - Audiophile
Information and Entertainment System
Pinpoint Tests
Pinpoint Test D: The Subwoofer Is Inoperative/Does Not Operate Correctly - Audiophile
Refer to Wiring Diagrams Set 130, Audio System for schematic and connector information. Diagrams By Number
Normal Operation
The subwoofer amplifier receives voltage through circuit SBP38 (BN/RD) and ground through circuit GD161 (BK/YE). The subwoofer amplifier and the subwoofer speaker cannot be replaced individually.
To enable the subwoofer amplifier, the Audio Control Module (ACM) sends voltage through the enable/clip circuit SME23 (VT/RD). The circuit acts as both an output (to enable the amplifier) and an input (to detect an amplifier overload condition). A variable resistor in the subwoofer amplifier modifies the voltage signal from the ACM. In the event of an overload, the ACM clips the audio output signal to the amplifier (heard as distortion), in order to prevent damage to the amplifier and speakers.
The clip/enable status is based on the following voltages, as detected by the ACM:
- Less than 0.4 volts: amplifier disabled
- Between 3.8 and 6.7 volts: amplifier enabled
- Greater than 8.5 volts: amplifier clipped
An open in circuit SME23 (VT/RD) causes the subwoofer to produce no sound, because the enable signal does not reach the subwoofer amplifier. A short to ground or short to voltage can cause severe distortion to be heard in the subwoofer.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Subwoofer
- ACM
PINPOINT TEST D: THE SUBWOOFER IS INOPERATIVE/DOES NOT OPERATE CORRECTLY - AUDIOPHILE
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
NOTE: Failure to disconnect the battery when instructed will result in false resistance readings. Refer to Battery.
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D1 CHECK CIRCUIT SBP38 (BN/RD) FOR VOLTAGE
- Ignition OFF.
- Disconnect: Subwoofer C466.
- Measure the voltage between the subwoofer C466-5, circuit SBP38 (BN/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to D2.
No
VERIFY the Smart Junction Box (SJB) fuse 38 (20A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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D2 CHECK CIRCUIT GD161 (BK/YE) FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the subwoofer C466-2, circuit GD161 (BK/YE), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to D3.
No
REPAIR the circuit. TEST the system for normal operation.
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D3 CHECK CIRCUIT SME23 (VT/RD) FOR VOLTAGE
- Connect: Negative Battery Cable.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the subwoofer C466-1, circuit SME23 (VT/RD), harness side and ground.
- Is the voltage between 3.8 and 6.7 volts?
Yes
GO to D6.
No
GO to D4.
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D4 CHECK CIRCUIT SME23 (VT/RD) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM C240c.
- Ignition ON.
- Measure the voltage between the subwoofer C466-1, circuit SME23 (VT/RD), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to D5.
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D5 CHECK CIRCUIT SME23 (VT/RD) FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the subwoofer C466-1, circuit SME23 (VT/RD), harness side and the ACM C240c-4, circuit SME23 (VT/RD), harness side; and between the subwoofer C466-1, circuit SME23 (VT/RD), harness side and ground.
- Is the resistance less than 5 ohms between the subwoofer and the ACM, and greater than 10,000 ohms between the subwoofer and ground?
Yes
GO to D9.
No
REPAIR the circuit. TEST the system for normal operation.
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D6 CHECK THE AUDIO SIGNAL TO THE SUBWOOFER
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the AC voltage between the subwoofer C466-7, circuit VME22 (VT/GN), harness side and the subwoofer C466-8, circuit RME22 (GN/WH), harness side.
- Is a fluctuating AC voltage present?
Yes
INSTALL a new subwoofer. REFER to Subwoofer Subwoofer. TEST the system for normal operation.
No
GO to D7.
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D7 CHECK THE AUDIO CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM C240c.
- Ignition ON.
- Measure the voltage between the subwoofer C466-7, circuit VME22 (VT/GN), harness side and ground; and between the subwoofer C466-8, circuit RME22 (GN/WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit in question. TEST the system for normal operation.
No
GO to D8.
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D8 CHECK THE AUDIO CIRCUITS FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the subwoofer, harness side and the ACM, harness side; and between the subwoofer, harness side and ground as follows:
- Is the resistance less than 5 ohms between the subwoofer and the ACM, and greater than 10,000 ohms between the subwoofer and ground?
Yes
GO to D9.
No
REPAIR the circuit in question. TEST the system for normal operation.
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D9 CHECK FOR CORRECT ACM OPERATION
- Ignition OFF.
- Disconnect all the ACM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM connectors and make sure they seat correctly.
- Operate the system and determine if the concern is still present.
- Is the concern still present?
Yes
INSTALL a new ACM. REFER to Audio Control Module (ACM) Audio Control Module (ACM). TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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