GM Service Manual Online
For 1990-2009 cars only

Schematic Reference: Radio/Audio System Schematics

Diagnostic System Check - Entertainment System

Always perform the Vehicle Diagnostic System Check before proceeding with these diagnostic procedures. Refer to Diagnostic System Check - Vehicle .

One Speaker Inoperative

Important: The following information lists the most probable cause of the concern to the least probable cause. If the list leads to the replacement of a component, always inspect for a poor connection before proceeding with replacement. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

With RPO UZ6

    • Speaker output open--Test the appropriate speaker output circuits for an open. Refer to Circuit Testing and Wiring Repairs .
    • No audio output from the radio--Disconnect speaker harness connector from speaker. Turn On the radio and adjust volume approximately 50 percent. Measure the A/C voltage across the speaker harness connector terminals. Replace the speaker if A/C voltage is present. Refer to Radio Front Side Door Lower Speaker Replacement , Front Upper Speaker Replacement , or Radio Rear Speaker Replacement .
    • If no A/C voltage is present, replace the radio. Refer to Control Module References for replacement, setup, and programming.
    • Perform the vehicle identification number (VIN) Relearn procedure with a scan tool. On the scan tool, go to Module Replacement/Setup in Vehicle Control Systems and select Radio.

In the Monsoon radio system (U85) the front door tweeters and rear midrange speakers are coupled together inside the amplifier on the same bridge. Similarly, the front door lower speakers and the rear subwoofers are coupled together within the amplifier. Therefore it is possible to have a concern with one of the channels, wires, or speakers that affect the operation of one or all of the channels that use the same bridge. For example, a concern that causes distortion in a dominate midrange speaker may be caused by a problem with the coupled speaker on that circuit.

With RPO U85

    • Speaker output circuit from amplifier open or shorted--Test the appropriate speaker output circuits for an open or short. Refer to Circuit Testing and Wiring Repairs .
    • No low level audio output from the radio--Test for any AC voltage between the appropriate low level output circuits at the amplifier harness connector, disconnected with the radio volume adjusted to an audible level. If no A/C voltage is present, replace the radio. Refer to Radio Replacement .
    • No audio output from the amplifier--Test for any A/C voltage between the appropriate speaker output circuits at the speaker harness connector, disconnected with the radio volume adjusted to an audible level. If A/C voltage is present, replace the speaker. If no A/C voltage is present, replace the amplifier. Refer to Radio Speaker Amplifier Replacement .

Speakers - One Channel Inoperative

Important: The following information lists the most probable cause of the concern to the least probable cause. If the list leads to the replacement of a component, always inspect for a poor connection before proceeding with replacement. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Important: The following procedure assumes all speakers are operative for all modes of operation except digital radio.

With RPO U2K

    • Audio signal circuit open--Test the appropriate audio signal circuit between the radio and digital radio receiver (DRR) for an open, short to ground, or short to battery. Refer to Circuit Testing and Wiring Repairs .
    • No audio output from the DRR--Measure the voltage from the DRR audio signal circuit with the radio ON. Replace the DRR if no voltage is measured. Refer to Digital Radio Receiver Replacement and Digital Radio Receiver Setup .
    • No audio input to the radio--Measure the voltage from the radio audio signal circuit with the radio ON. Replace the radio if voltage is measured and symptom is still present. Refer to Control Module References for replacement, setup, and programming.
    • After replacing the radio, perform the VIN Relearn procedure. On the scan tool, go to Module Replacement/Setup in Vehicle Control Systems and select Radio.