Pinpoint Test C: Poor Quality/Distorted/No Sound From One Or More Speakers

Information and Entertainment System

Pinpoint Tests

Pinpoint Test C: Poor Quality/Distorted/No Sound From One Or More Speakers

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

Normal Operation

When the key is placed in START, voltage is sent to the audio unit through the START sense circuit. When the audio unit receives this signal, it mutes the speaker signals. After the key is removed from START, the audio unit directs audio signals to the speakers through separate positive and negative circuits. The audio unit provides internal circuit protection for shorts to ground, shorts to voltage, or shorts between any output circuits.

In addition, a short on an individual speaker circuit can cause all speakers to lose sound due to the built-in overload protection feature of the audio unit.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors
- Speaker
- Audio unit

PINPOINT TEST C: POOR QUALITY/DISTORTED/NO SOUND FROM ONE OR MORE SPEAKERS

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: Use the speaker walk-around test to determine which speaker(s) has a concern.

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C1 CHECK THE SPEAKER CIRCUITS FOR A SHORT TO VOLTAGE


- Ignition OFF.
- Disconnect: Audio Unit C290a (Except Base).
- Disconnect: Audio Unit C240 (Base).
- Disconnect: Suspect Speaker(s).
- Ignition ON.
- Measure the voltage between the suspect speaker, harness side and ground as follows:









- Is any voltage present?

Yes
REPAIR the circuit in question. TEST the system for normal operation.

No
GO to C2.

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C2 CHECK THE SPEAKER CIRCUITS FOR AN OPEN OR SHORT TO GROUND


- Ignition OFF.
- Measure the resistance between the audio unit, harness side and the suspect speaker, harness side; and between the audio unit, harness side and ground as follows:









- Is the resistance less than 5 ohms between the audio unit and the suspect speaker, and greater than 10,000 ohms between the audio unit and ground?

Yes
GO to C3.

No
REPAIR the circuit in question. TEST the system for normal operation.

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C3 CHECK THE SPEAKER


- Connect: Audio Unit C290a (Except Base).
- Connect: Audio Unit C240 (Base).
- Substitute a known good speaker for the suspect speaker.
- Operate the audio unit in radio tuner mode.
- Is the sound quality OK?

Yes
INSTALL a new speaker. REFER to Door Speaker Door Speaker or Parcel Shelf Speaker Parcel Shelf Speaker. TEST the system for normal operation.

No
INSTALL a new audio unit. REFER to Audio Unit Service and Repair. TEST the system for normal operation.

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