Identifying Concerns

Error Codes:

- Examine the technical service bulletins. Examine the Dealer Communication System for any applicable Preliminary Information (P/I) for customer concerns.
- For reception concerns, determine if the station is obtainable in the customer's listening area.
- Test for audio reception/noise by positioning the vehicle outside of the building with the engine compartment lid down.
- Duplicate the customer's concern before trying to diagnose the system. Ask the customer to demonstrate the condition. Test drive the vehicle with the customer, and then test drive another similar model vehicle (with a similar audio system). Compare the two vehicles in order to determine if the condition is abnormal.
- Before diagnosing, identify the components, their features, and 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 switch position in which the noise appears:
^ Accessory
^ ON (engine not running)
^ ON (engine running)
2. Remove fuses one at a time until the noise condition has been eliminated.
3. Mark the suspected fuse.
4. Reinstall all fuses and circuit breakers.
5. Refer to Power Distribution Schematics in Diagrams in order to identify all systems and components powered by the suspected fuse.
6. Disconnect the components powered by the suspected fuse, one at a time until the noise condition has been eliminated and the noisy component is identified.
7. Inspect the ground integrity of the component causing the condition.
- 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 normal.
- 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.