Identifying Concerns

^ CHECK for technical service bulletins. Check the Dealer Communication System for any applicable Preliminary Information (P/I) for customer concerns.
^ CHECK for stored diagnostic trouble codes. Refer to Computer and Control Systems. Computers and Control Systems
^ For reception concerns, determine if the station is obtainable in the customer's listening area.
^ To test for audio reception/noise, position the vehicle outside of the building with the hood down.
^ Duplicate the customer's complaint before trying to diagnose the system. Have the customer demonstrate the condition. Test drive the vehicle with the customer and then test drive another similar model vehicle (with a similar audio system) to do a comparison of the two vehicles to determine if the condition is abnormal.
^ Before diagnosing, identify components, their features and the customer's complaint.
^ Determine if any aftermarket equipment is installed on the vehicle. Disconnect the aftermarket equipment and determine if the customer's complaint still exists. Follow GM guidelines for installation of aftermarket components.
^ Perform the following steps to identify a noisy component:
1. Identify ignition key switch position in which the noise appears, such as: accessory, key ON engine not running, and key ON engine running.
2. REMOVE fuses one at a time until the complaint condition has been eliminated.
3. Mark the complaint fuse(s) and reinstall all fuses.
4. Refer to Power and Ground Distribution Diagnosis to identify all systems and components powered by the complaint fuse(s). Power and Ground Distribution
5. Disconnect the components powered by the complaint fuse(s) one at a time until the complaint condition has been eliminated and the noisy component is identified.
6. CHECK the ground integrity of the complaint causing component.
^ An interference condition is NOT necessarily an audible noise.
^ Most noises can be found on weak stations near the low end of the band and are considered to be a normal condition.
^ Ignition noise on FM could indicate a possible defective ignition system.
^ Malfunctioning and marginal components, relays, and solenoids may induce noise and/or poor reception.