For 1990-2009 cars only
Begin by performing the following steps:
- Verify the customer complaint.
- Follow radio service procedures.
- If technical assistance is required, have all of the pertinent information available before placing the telephone call.
Identifying Concerns
| • | Check for technical service bulletins. Check the dealer communication system for any applicable preliminary information for customer concerns. |
| • | Check for stored diagnostic trouble codes. Refer to Drivability and Emissions in Engine 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 the building with the hood down. |
| • | Duplicate the customer's complaint before trying to diagnose the system . Test drive the vehicle with the customer. Afterward, test drive another similar model vehicle with a similar audio system. Compare the two test drives in order to determine whether the condition is abnormal. |
| • | Before diagnosing, identify the components, their features and the customer's complaint. |
| • | Determine whether any aftermarket equipment is installed in the vehicle. Disconnect any such aftermarket equipment and determine whether the customer's complaint 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. Examples of key switch positions include the following: |
| • | Accessory |
| • | Key ON with the engine not running |
| • | Key ON with the engine running |
| 2. | Remove the fuses one at a time until the complaint condition has been eliminated. |
| 3. | Mark the complaint fuses. Reinstall all of the fuses and circuit breakers. |
| 4. | Refer to Power Distribution and Fuse Block Details in Electrical Diagnosis in order to identify all systems and components powered by the complaint fuses. |
| 5. | Disconnect the components powered by the complaint fuses one at a time until the complaint condition has been eliminated and the noisy component has been identified. |
| 6. | Check the ground integrity of the component which caused the complaint. |
| • | An interference condition is NOT necessarily an audible noise. |
| • | Most noises can be found on weak stations near the low end of the band. These noises are considered a normal condition. |
| • | Ignition noise on the FM band could indicate a possible defective ignition system. |
| • | Noise or poor reception could be caused by any of the following: |
| - | Malfunctioning or marginal components |
| - | Malfunctioning or marginal relays |
| - | Malfunctioning or marginal solenoids. |
Corrective Action
| • | Use the proper tools for diagnostics and repairs. |
| • | Follow the ESD Guidelines. |
| • | Use the available noise suppression devices: |
| - | 220 mF (50V) capacitor GM P/N 1227895 |
| - | .47mF capacitor GM P/N 122794 |
| - | Fuse block capacitor GM P/N 469328 |
| - | Feed through capacitor GM P/N 477371 |
| - | Filter Package GM P/N 1224205 |
| - | Turn signal suppression GM P/N 3861565 |
| - | Fuel pump suppressor GM P/N 25027405 |
| - | 21 inch (53cm) braided ground strap GM P/N 8910791 |
| - | 19 inch (48cm) braided ground strap GM P/N 6286800 |
| - | 10.5 inch (26.5cm) braided ground strap GM P/N 6287160 |
| - | 8.5 inch (21.5cm) braided ground strap GM P/N 12091511 |
| • | Utilize the test tape/CD diagnostic kit GM P/N J 39916-A in order to optimize proper audio diagnostics. |
| • | If the condition requires that the radio be sent in to the service center, describe the symptoms on the warranty form accurately. Along with the warranty form, send a copy of the service writer check list with the unit. |
| • | Do not leave a compact disc or tape in the car. Extreme heat can damage CDs and tapes. |
| • | Place any cassette tapes into their cases. Cassette tapes may be damaged if they are not stored in their cases. Vibrations caused by the vehicle can cause the tape to unwind inside the cartridge. |
| • | Use the trouble trees/noise charts in the DE SSG. |
| • | Before removing the speakers, check all of the connectors and wiring to the speakers. Examine the connectors for bent or loose pins. Refer to Troubleshooting Procedures in Electrical Diagnosis. |
| • | If a test antenna is used during diagnostics, ground the test antenna base to the vehicle body and do not hold the mast. |
Important
| • | Inspect the antenna coax connectors for corrosions, bad connections or bad crimps. Route the coax separately from the other wires. Shield the antenna coax interconnections with aluminum or nickel tape as described in the DE SSG. |
| • | Inspect all of the grounds, not just the radio and antenna grounds. Refer to the antenna diagnostic section. |
| • | Note that coated screws or bolts can act as poor grounds. |
| • | Always use a braided ground strap when applying grounds. Keep the ground strap as short as possible. The shorter the ground strap is, the better. |
| • | Use aluminum foil tape or nickel tape in order to shield against magnetically induced interference when shielding the following components: |
| - | The dash |
| - | The wires |
| - | The hoses (most hoses are conductive unless they have a white stripe) |
| • | For optimum results, try varying the following ground techniques: |
| - | Add a ground at both ends of the tape. |
| - | Add a ground at only one end of the tape. |
| - | Do not add a ground to the tape. |
| • | When shielding a harness with tape, attach a ground strap to the end of the tape and then wrap the strap 360 degrees around the tape. Secure the other end of the strap to a chassis ground which is known to be good. |
| • | Suppress any interference at its source, if possible. |
| • | Be careful when applying suppression. Signal wires, including sensor outputs, clock, and communications circuits, can not be suppressed. Battery and ignition wires can be suppressed. |
| • | After applying suppression, all vehicle systems should be checked for proper operation and function. This includes systems which are not related to the audio system. |
| • | Interference can usually be eliminated by shielding/grounding or suppression. |
| • | Note that capacitors work best on switch pops and low frequency noise. Filters work best on high frequency whines and static. |
| • | When possible, make a test harness that includes both capacitors and filters. Always check the effectiveness of and operation of such measures before permanently installing a fix. |
| • | Use the following recommended capacitor application for an audible pop induced from a switching operation: |
| - | Add a capacitor across the contacts of the switch. |
| - | Add a capacitor from the hot side of the switch to the ground. |
| - | Add a capacitor from each side of the switch to the ground |
| • | Perform the following checks if a complaint condition is only present with the ignition key in the RUN position and the engine running: |
| - | Check the integrity of the ignition system. Refer to Ignition System in Engine General Information and Mechanical Diagnosis. Examples of areas to examine include the following: |
| • | Proper spark plug wire routing |
| • | No misfiring |
| - | Check the integrity of the engine compartment grounds. |
| - | Check for malfunctioning relays, solenoids, or other components which may be inducing noise or poor reception. |
| - | Check the ground integrity of the component which is causing the complaint. |
| • | When the customer complaint includes noise or poor reception, perform the antenna system test and make any necessary repairs. |
Generator Whine Concerns
| • | Check the ground terminal on the battery. |
| • | Check for coated mounting bolts on the generator bracket. |
| • | Check for a faulty mounting of the generator to the engine. |
| • | Ensure that all of the ground straps between the engine and the frame are clean and tight. |
| • | Try the following fixes: |
| 1. | If the noise persists, check the charging system. Refer to Charging System in Engine Electrical. |
| 2. | If the charging system is functioning normally, check for technical service bulletins on generator whine. |
| 3. | Install a filter GM P/N 1224205 in the battery feed to the radio. |
| 4. | If installing the filter does not eliminate the noise, try installing the filter using the following variations: |
| - | Install the filter with the single wire side toward the radio and the ground wire attached to a good ground. |
| - | Remove the ground to the filter. |
| - | Reverse the filter so that the two wire side is toward the radio with the ground wire attached to a good ground. |
| - | Remove the ground from the filter. |
| 5. | If the noise is still present, install another filter GM P/N 1224205 in the ignition feed to the radio. Install this filter using the same variations as the described for the first filter in the previous step. |
| 6. | If the installation of the second filter causes turn On or turn OFF delays or other noticeable performance concerns, remove it. Install a .47mF capacitor to ground in the filter's place. |
| 7. | Remove any unneeded filters after the repairs are complete before reassembling the vehicle. |
| 8. | Refer to System Diagnosis. |
