Pinpoint Test E: Poor Quality/Distorted/No Sound From All Speakers - THX(R)
Information and Entertainment System
Pinpoint Tests
Pinpoint Test E: Poor Quality/Distorted/No Sound From All Speakers - THX(R)
Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information. Diagrams By Number
Normal Operation
The audio Digital Signal Processing (DSP) module is enabled by a enable/clip circuit. To enable the audio DSP module, the Audio Control Module (ACM) sends voltage through the enable/clip circuit. The circuit acts as both an output (to enable the audio DSP module) and an input (to detect an overload condition). The voltage sent by the ACM passes through a variable resistor in the audio DSP module, then to ground. As the audio DSP module reaches maximum output, the resistance in the variable resistor decreases. This decreases the voltage drop, resulting in the ACM detecting a higher voltage on the enable/clip circuit. When the voltage reaches the clip threshold, the ACM clips the audio output signal to the audio DSP module (heard as distortion), in order to prevent damage to the audio DSP module and the speakers.
The enable/clip status is based on the following voltages, as detected by the ACM:
- Less then 0.4 volt: amplifier disabled
- Between 3.8 and 6.7 volts: amplifier enabled
- Greater than 8.5 volts: amplifier clipped
For vehicles with Intelligent Access (IA), the Remote Function Actuator (RFA) module sends a voltage signal to the ACM when the ignition is in a START sequence. This prevents voltage spikes from creating a popping sound during engine cranking. However, if this circuit has a short to voltage or the RFA module sends the signal incorrectly, it results in the speaker output being muted.
B125C:11-B125C:15 / U0184:00-U0238:00:
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Audio DSP module
- ACM
PINPOINT TEST E: POOR QUALITY/DISTORTED/NO SOUND FROM ALL SPEAKERS - THX(R)
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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E1 CHECK THE START SIGNAL TO THE ACM
- Ignition OFF.
- Disconnect: ACM C2253a.
- Ignition ON.
- Measure the voltage between the ACM C2253a-15, circuit CBP28 (GY/VT), harness side and ground.
- Is any voltage present?
Yes
If the vehicle is equipped with Intelligent Access (IA), GO to E2.
Otherwise, REPAIR the circuit. TEST the system for normal operation.
No
If the vehicle is equipped with IA, GO to E3.
Otherwise, GO to E4.
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E2 CHECK THE START SIGNAL FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: RFA Module C2153d.
- Measure the voltage between the ACM C2253a-15, circuit CBP28 (GY/VT), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. CLEAR the DTCs. REPEAT the RFA module self-test. TEST the system for normal operation.
No
INSTALL a new RFA module. TEST the system for normal operation.
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E3 CHECK THE START SIGNAL FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: RFA Module C2153d.
- Ignition ON.
- Measure the resistance between the ACM C2253a-15, circuit CBP28 (GY/VT), harness side and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to E4.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the RFA module self-test. TEST the system for normal operation.
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E4 CHECK THE AUDIO DSP MODULE VOLTAGE SUPPLY
- Ignition OFF.
- Disconnect: Audio DSP Module C4326c.
- Measure the voltage between the audio DSP module, harness side and ground as follows:
- Are the voltages greater than 10 volts?
Yes
GO to E5.
No
VERIFY the Smart Junction Box (SJB) fuse 38 (20A) or fuse 40 (20A) is OK. If OK, REPAIR the circuit in question. 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.
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E5 CHECK THE AUDIO DSP MODULE GROUND FOR AN OPEN
- Disconnect: Negative Battery Cable.
- Measure the resistance between the audio DSP module, harness side and ground as follows:
- Are the resistances less than 5 ohms?
Yes
GO to E6.
No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
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E6 CHECK THE AUDIO DSP MODULE ENABLE CIRCUIT FOR CORRECT VOLTAGE
- Connect: Negative Battery Cable.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the audio DSP module C4326a-3, circuit CME31 (BU/GN), harness side and ground.
- Is the voltage between 3.8 and 6.7 volts?
Yes
GO to E10.
No
GO to E7.
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E7 CHECK THE AUDIO DSP MODULE ENABLE CIRCUIT FOR A SHORT TO VOLTAGE
- Disconnect: ACM C2253a.
- Ignition ON.
- Measure the voltage between the audio DSP module C4326a-3, circuit CME21 (BU/GN), harness side and ground.
- Is any voltage present?
Yes
REPAIR the circuit. TEST the system for normal operation.
No
GO to E8.
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E8 CHECK THE AUDIO DSP MODULE ENABLE CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between the audio DSP module C4326a-3, circuit CME31 (BU/GN), harness side and the ACM C2253a-7, circuit CME31 (BU/GN), harness side; and between the audio DSP module C4326a-3, circuit CME31 (BU/GN), harness side and ground.
- Is the resistance less than 5 ohms between the audio DSP module and the ACM, and greater than 10,000 ohms between the audio DSP module and ground?
Yes
GO to E9.
No
REPAIR the circuit. TEST the system for normal operation.
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E9 CHECK FOR CORRECT ACM OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the ACM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect 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). CLEAR any DTCs present. 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. CLEAR any DTCs present. TEST the system for normal operation.
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E10 CHECK FOR CORRECT AUDIO DSP MODULE OPERATION
- Ignition OFF.
- Connect: All Disconnected Connectors.
- Disconnect all the audio DSP module connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the audio DSP 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 audio DSP module. REFER to Audio Digital Signal Processing (DSP) Module Audio Digital Signal Processing (DSP) Module. CLEAR any DTCs present. 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. CLEAR any DTCs present. TEST the system for normal operation.
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