1. Connect a scan tool.
2. Turn the ignition switch ON.
3. Attempt to establish communication with the flowing modules:

-	Radio (IRC).

-	Radio amplifier (AMP).

Does the scan tool communicate with both the radio and the radio amplifier?

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Go to Step 4

Go to Step 2

Does the scan tool communicate with the radio amplifier but not the radio?

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Go to Radio/Audio System Check

Go to Step 3

Does the scan tool communicate with the radio but not the radio amplifier?

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Go to Radio/Audio System Check

Go to Scan Tool Does Not Communicate with Class 2 Data Line in Data Link Communications

Check for diagnostic trouble codes (DTCs) In the flowing modules:

1. Radio (IRC).
2. Radio amplifier (AMP).

Are any DTCs stored?

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Go to Step 5

Go to Radio/Audio System Check

Are any Loss of Class 2 Serial Data Communication DTCs set? (Loss of Class 2 Serial Data Communication DTCs have the form UXXXX.)

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Go to Diagnostic Trouble Code (DTC) List in Data Link Communications

Go to Diagnostic Trouble Code (DTC) List/Type