Identifying Concerns

^ Examine the technical service bulletins. Use the dealer communication system for any applicable preliminary information (P/I) for customer concerns.
^ Inspect for stored diagnostic trouble codes.
^ For reception concerns, determine if the station is obtainable in the customer's listening area.
^ When you 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. Instruct the customer to demonstrate the condition. Test drive the vehicle with the customer, then test drive a similar model (with a similar audio system) in order to determine if the condition is abnormal.
^ Before you diagnose the condition, identify the following:
- The components
- The component features
- The customer's complaint
^ Determine if any aftermarket equipment is installed on the vehicle. Disconnect the aftermarket equipment in order to determine if the customer's complaint still exists. Follow GM guidelines for the 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:
^ The accessory
^ The key ON engine not running
^ The key ON engine running
2. Remove the fuses one at a time until the condition is eliminated.
3. Mark the complaint fuses and reinstall all the fuses and the circuit breakers.
4. Refer to Power Distribution and Fuse Block Details in Electrical Diagnosis in order to identify all the systems and the components powered by the complaint fuses.
5. Disconnect the components powered by the complaint fuses one at a time until the condition is eliminated and the noisy component is identified.
6. Inspect the ground integrity of the questionable 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. This is considered to be a normal condition.
^ Ignition noise on FM could indicate that the ignition system is faulty.
^ The following conditions may induce noise or poor reception:
- Malfunctioning and marginal components
- Relays
- Solenoids