RFI Determination and Identifying Chart

This chart is to be used along with the diagnostic charts to help determine if the condition is RFI related, and to help identify what electronic device in the vehicle is interfering with the radio. Make sure the information in the questionnaire is as accurate as possible. You MUST be able to duplicate the customer's condition to diagnose RFI concerns.

The process of identifying RFI and the source of an interference is simply the process of elimination. When the source of the interference is disconnected from power, the radio will work properly.

Box 1

Verify that the condition is present, then disconnect any non-factory add-on electronics, (not including the radio)

Box 2

If the condition goes away when a particular device is disconnected, reconnect the device to verify it as the source of the interference. If the condition is related to non-factory add-on electronics, consult the GM installation guidelines (See Box 6) as an example of how to add an electronic component to the vehicle's electrical system.

Box 3

If the condition is ONLY present with the engine running, disconnect electrical components that are active only with the engine running. The charging system, various solenoids, and relays may be intermittently disconnected while observing the condition. In some cases a component cannot be disconnected while the engine is running. In these cases, the component can be tested independent of the vehicle (i.e. fuel injectors). For further tips on engine noise diagnostics refer to the Delco Sound Service Guide, Engine Noise Chart.

Box 4

If the condition can be eliminated and the interference isolated to a component, determine if a bulletin has been published concerning this particular condition. Contact your Technical Assistance Group for additional information if no bulletins are found.

Box 5

If the concern cannot be eliminated by testing in any key position and by disconnecting fuses and components, the condition most likely is not RFI.

Refer to the Delco Sound Service Guide or the vehicle service manual for further diagnostic tips and check for any published bulletins. If the concern cannot be identified or eliminated, contact your Technical Assistance Group for further assistance.

Box 6

The "Installation Guidelines for Aftermarket Accessories" for all model years and all trucks and carlines are located in the following Service Bulletin 91-8-2.

Also, there may be separate installation guidelines for cellular phones. A search for service bulletins may be necessary to find these.