Pinpoint Test E: The Subwoofer Is Inoperative
Information and Entertainment System
Pinpoint Test E: The Subwoofer Is Inoperative
Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information Electrical Diagrams.
Normal Operation - MKX Premium Audio
To enable the subwoofer amplifier, the Audio Control Module (ACM) sends voltage through the enable/clip circuit. The circuit acts as both an output (to enable the amplifier) and an input (to detect an amplifier overload condition). The voltage sent by the ACM (Audio Control Module) passes through a variable resistor in the subwoofer amplifier, then to ground. As the amplifier reaches maximum output, the resistance in the variable resistor decreases. This decreases the voltage drop, resulting in the ACM (Audio Control Module) detecting a higher voltage on the enable/clip circuit. When the voltage reaches the clip threshold, the ACM (Audio Control Module) clips the audio output signal to the amplifier (heard as distortion), to prevent damage to the amplifier and speakers.
The enable/clip status is based on the following voltages, as detected by the ACM (Audio Control Module) :
- Less then 0.4 volt: amplifier disabled
- Between 3.8 and 6.7 volts: amplifier enabled
- Greater than 8.5 volts: amplifier clipped
An open in the enable/clip circuit 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.
The subwoofer amplifier and subwoofer speaker are integral to the enclosure and cannot be serviced separately.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Subwoofer
- ACM (Audio Control Module)
PINPOINT TEST E : THE SUBWOOFER IS INOPERATIVE
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 results in false resistance readings.
E1 CHECK THE AUDIO SIGNAL TO THE SUBWOOFER
- Ignition OFF.
- Disconnect: Subwoofer C4208.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the AC voltage between the subwoofer C4208-7, circuit VME22 (VT/GN), harness side; and between the C4208-8, circuit RME22 (GN/WH), harness side.
Is a fluctuating AC voltage present?
Yes
GO to E2.
No
GO to E7.
E2 CHECK THE SUBWOOFER VOLTAGE SUPPLY
- Ignition ON.
- Measure the voltage between the subwoofer C4208-5, circuit SBP05 (GY/RD), harness side and ground.
Is the voltage greater than 10 volts?
Yes
GO to E3.
No
VERIFY the Body Control Module (BCM) fuse 5 (20A) is OK. If OK, REPAIR the circuit. CLEAR any DTCs present. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams.
E3 CHECK THE SUBWOOFER GROUND CIRCUIT FOR CONTINUITY
- Ignition OFF.
- Disconnect: Negative Battery Cable.
- Measure the resistance between the subwoofer C4208-2, circuit GD148 (BK/YE), harness side and ground.
Is the resistance less than 5 ohms?
Yes
GO to E4.
No
REPAIR the circuit for an open. TEST the system for normal operation.
E4 CHECK THE SUBWOOFER ENABLE CIRCUIT FOR CORRECT VOLTAGE
- Connect: Negative Battery Cable.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the subwoofer C4208-1, circuit SME56 (BN), harness side and ground.
Is the voltage between 3.8 and 6.7 volts?
Yes
INSTALL a new subwoofer. REFER to Speaker - Subwoofer . CLEAR any DTCs present. TEST the system for normal operation.
No
GO to E5.
E5 CHECK THE SUBWOOFER ENABLE CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM (Audio Control Module) C240A.
- Ignition ON.
- Measure the voltage between the subwoofer C4208-1, circuit SME56 (BN), harness side and ground.
Is any voltage present?
Yes
REPAIR the circuit for a short to voltage. TEST the system for normal operation.
No
GO to E6.
E6 CHECK THE SUBWOOFER ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the subwoofer C4208-1, circuit SME56 (BN), harness side and the ACM (Audio Control Module) C240A-7, circuit SME56 (BN), harness side; and between the subwoofer C4208-1, circuit SME56 (BN), harness side and ground.
Is the resistance less than 5 ohms between the subwoofer and the ACM (Audio Control Module), and greater than 10,000 ohms between the subwoofer and ground?
Yes
GO to E9.
No
REPAIR the circuit. TEST the system for normal operation.
E7 CHECK THE AUDIO CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: ACM (Audio Control Module) C240B.
- Ignition ON.
- Measure the voltage between the subwoofer C4208-7, circuit VME22 (VT/GN), harness side and ground; and between the subwoofer C4208-8, circuit RME22 (GN/WH), harness side and ground.
Is any voltage present?
Yes
REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation.
No
GO to E8.
E8 CHECK THE AUDIO CIRCUITS FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the subwoofer C4208-7, circuit VME22 (VT/GN) and the ACM (Audio Control Module) C240B-4, circuit VME22 (VT/GN).
- Measure the resistance between the subwoofer C4208-8, circuit RME22 (GN/WH) and the ACM (Audio Control Module) C240B-17, circuit RME22 (GN/WH).
Is the resistance less than 5 ohms between the subwoofer and the ACM (Audio Control Module) or audio DSP (Digital Signal Processing) module and greater than 10,000 ohms between the subwoofer and ground?
Yes
GO to E9.
No
REPAIR the circuit in question. CLEAR any DTCs present. TEST the system for normal operation.
E9 CHECK FOR CORRECT ACM (Audio Control Module) OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the ACM (Audio Control Module) connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the ACM (Audio Control Module) 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 (Audio Control Module). REFER to 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.