Pinpoint Test D: Poor Quality/Distorted/No Sound From All Speakers - THX(R) Audio System

Information and Entertainment System

Pinpoint Tests

Pinpoint Test D: Poor Quality/Distorted/No Sound From All Speakers - THX(R) Audio System

Refer to Wiring Diagram Set 130, Audio System/Navigation for schematic and connector information. Diagrams By Number

Normal Operation

The Audio Control Module (ACM) enables the audio Digital Signal Processing (DSP) module through circuit CME27 (YE/VT). The audio DSP module receives voltage through circuits SBB20 (GN/RD) and SBB21 (GY/RD), and ground through circuit GD148 (BK/YE).

Left and right channel audio signals are sent from the ACM to the audio DSP module through circuits VME17 (GN), RME17 (GY), VME18 (VT) and RME18 (YE). If there is a fault on one of these circuits, the audio quality will be reduced approximately 25% for all speakers.

A short to ground or short to voltage in the circuitry to the audio DSP module can cause multiple speakers to lose sound due to the built-in overload protection feature of the ACM. In this case, a speaker fault DTC will set, and this pinpoint test should be followed to isolate the damaged circuit.

The enable/clip circuit CME27 (YE/VT) carries out 2 functions: to turn the audio DSP module on, and to monitor an overload condition to the audio DSP module. In the event of an overload, the ACM clips the audio output signal to the audio DSP module (heard as distortion).

- DTC B2965 (Audio System Speaker Circuit Failure) - sets when an open or a short to ground is detected on any of the audio output circuits to the audio DSP module; therefore, the fault can be isolated to the circuitry from the ACM to the audio DSP module.
- DTC U0238 (Lost Communication With Digital Audio Control Module "D" (DSP)) - set by the ACM when status messages from the audio DSP module are missing for greater than 5 seconds with the ignition in the RUN position. Audio may still be produced, but the sound quality will be compromised.

This pinpoint test is intended to diagnose the following:

- Fuse
- Wiring, terminals or connectors
- Audio DSP module
- ACM

PINPOINT TEST D: POOR QUALITY/DISTORTED/NO SOUND FROM ALL SPEAKERS - THX(R) AUDIO SYSTEM

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 CIRCUITS SBB20 (GN/RD) AND SBB21 (GY/RD) FOR VOLTAGE

- Ignition OFF.
- Disconnect: Audio DSP Module C4326b.
- Measure the voltage between the audio DSP module, harness side and ground as follows:

- Are the voltages greater than 10 volts?

Yes
GO to D2.

No
VERIFY the Battery Junction Box (BJB) fuse 20 (20A) or fuse 21 (20A) is OK. If OK, REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.

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D2 CHECK CIRCUIT GD148 (BK/YE) 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 D3.

No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.

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D3 CHECK CIRCUIT CME27 (YE/VT) FOR VOLTAGE

- Connect: Negative Battery Cable.
- Connect: Audio DSP Module C4326b.
- Disconnect: Audio DSP Module C4326c.
- Operate the audio system in radio tuner (AM/FM) mode.
- Measure the voltage between the audio DSP module C4326c-3, circuit CME27 (YE/VT), 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 CME27 (YE/VT) FOR A SHORT TO VOLTAGE

- Ignition OFF.
- Disconnect: ACM C240d or C290d.
- Ignition ON.
- Measure the voltage between the audio DSP module C4326c-3, circuit CME27 (YE/VT), 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 CME27 (YE/VT) FOR AN OPEN OR SHORT TO GROUND

- Ignition OFF.
- Measure the resistance between the audio DSP module C4326c-3, circuit CME27 (YE/VT), harness side and the ACM C240d-4, circuit CME27 (YE/VT), harness side; and between the audio DSP module C43263-3, circuit CME27 (YE/VT), harness side and ground.

- Is a fluctuating AC voltage present?

Yes
GO to D9.

No
GO to D7.

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D7 CHECK THE AUDIO CIRCUITS TO THE AUDIO DSP MODULE FOR A SHORT TO VOLTAGE

- Ignition OFF.
- Disconnect: ACM C240a or C290a.
- Ignition ON.
- Measure the voltage between the Audio DSP module, harness side and ground as follows:

- Is any voltage present?

Yes
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.

No
GO to D8.

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D8 CHECK THE AUDIO CIRCUITS TO THE AUDIO DSP MODULE FOR AN OPEN OR SHORT TO GROUND

- Ignition OFF.
- Measure the resistance between the audio DSP module, harness side and the ACM, harness side; and between the audio DSP module, harness side and ground as follows:

- 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 D10.

No
REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.

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D9 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 the ACM DTCs. REPEAT the self-test.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.

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D10 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 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) - MKZ . 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 the DTCs. REPEAT the self-test.

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