Identifying Concerns

^ Inspect for technical service bulletins. Inspect the dealer communication system for any applicable Preliminary Information (P/I) for customer concerns.
^ Inspect for stored diagnostic trouble codes. Refer to A Powertrain On Board Diagnostic (OBD) System Check 4.3L or A Powertrain On Board Diagnostic (OBD) System Check 5.0/5.7L or A Powertrain On Board Diagnostic (OBD) System Check 6.5L Diesel or A Powertrain On Board Diagnostic (OBD) System Check 7.4L in Computers and Controls.
^ For reception concerns, determine if the station is obtainable in the customer's listening area.
^ In order to test for audio reception/noise, position the vehicle outside of the building with the hood down.
^ Duplicate the customer's concern before you 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) in order to make a comparison of the two vehicles. This helps determine if the condition is abnormal.
^ Identify the components and the features of the components before you diagnose the customer's concern.
^ Determine if any aftermarket equipment is installed on the vehicle. Disconnect the aftermarket equipment and determine if the customer's concern still exists. Follow GM guidelines for installation of aftermarket components.
^ Perform the following steps in order to identify a noisy component:
1. Identify the ignition key switch position in which the noise appears, such as accessory, key ON engine not running, and key ON engine running.
2. Determine if noise is Speaker Noise - Frontway, Speaker Noise - Sideways, or Speaker Noise - Backway before proceeding with the remaining steps.
3. Remove the fuses one at a time until the concern condition has been eliminated.
4. Mark the concern fuse(s). Reinstall all of the fuses.
5. Disconnect the components powered by the concern fuse(s) one at a time until you eliminate the concern condition. This will identify the noisy component.
6. Inspect the ground integrity of the concern causing component.
^ An interference condition is not necessarily an audible noise.
^ Most noises are on weak stations near the low end of the band. These noises are a normal condition.
^ Ignition noise on FM possibly indicates a faulty ignition system.
^ Malfunctioning and marginal components, relays, and solenoids may induce noise and/or poor reception.