Audio System Troubleshooting Hints
Audio System Troubleshooting Hints
Many conditions that affect radio operation may be corrected without removing the radio from the car. Verify the condition, and follow the diagnostic procedures in order to isolate and correct the condition. In order to properly diagnose any audio system problems, ensure that you have a fully charged battery.
Preliminary Inspections
Tools Required
J 39916-A CD and Cassette Diagnostic Audio Kit
Important: When testing the audio system for poor reception or noise, the vehicle should be outside away from metal buildings and utility lines, with the hood and rear compartment closed.
* Inspect for aftermarket electronic equipment that may have been installed on the vehicle. Temporarily disconnect the aftermarket electronic equipment to determine if it is the source of the noise.
* For reception concerns, first determine if the customer is within the listening area of the stations they are attempting to receive.
* Stations at the lower end of the FM band are more susceptible to audio noises than stations at the higher end.
* Ignition noise on the FM band may be an indication of an ignition system problem.
* Inspect the antenna coaxial connectors for corrosion or poor connections.
* Inspect all antenna, radio, and chassis grounds to ensure they are tight and free of corrosion.
* Inspect the rear defogger grid lines for large breaks or dark spots.
* Inspect the connections at the radio antenna module, if equipped, to ensure that they are clean and tight.
* If the noise is only from one speaker check for the following before speaker replacement:
- Isolate the noise using the J 39916-A.
- Inspect the speaker connections to ensure they are clean and tight.
- Inspect for a loose or incorrectly installed speaker or surrounding trim. Loose trim can cause a buzz or flutter which sounds like a malfunctioning speaker.
* Compare the customers vehicle to another similar model vehicle (with a similar audio system) to determine if the condition is abnormal.
Identifying Concerns
In order to isolate the source of the noise/poor reception, identify the ignition switch position that the concern is most noticeable.
1. Turn the ignition switch to the accessory position.
2. Turn ON the radio.
3. Seek up 88 to 108 FM then 550 to 1600 AM.
4. Record the number of valid radio stations where the tuner stops.
5. Listen for various noise problems.
Repeat these steps with the ignition switch in the ON position. Then repeat these steps again but with the engine running.
1. Return the ignition switch to the position that the concern was most noticeable.
2. Remove fuses or circuit breakers one at a time until the noise has been eliminated.
3. Identify what systems or components are powered by the fuse.
4. Reinstall all fuses and circuit breakers.
5. Disconnect the components powered by the fuse one at a time until the concern has been eliminated.
6. Refer to corrective action for tips on eliminating noise concerns.
For noise concerns not identified using prior procedure, perform the following.
1. Turn the ignition switch to the position the concern was most noticeable.
2. Turn ON the radio.
3. Slowly remove the radio from the mounting bracket.
4. If noise is greatly reduced, the noise is most likely caused by wiring harnesses or hoses behind or on top of radio or antenna coax cable. The harness or hoses need to be rerouted or wrapped with aluminum or nickel tape to shield. Refer to corrective action for additional tips on eliminating noise concerns.
For noise concerns not identified using prior procedure, perform the following:
1. Turn the ignition switch to the position the concern was most noticeable.
2. Turn ON the radio.
3. Remove the radio and unplug the antenna coax cable from the radio.
4. If noise is eliminated, the noise is most likely caused by a degraded antenna system (poor antenna ground plane, radio case ground or corrosion at antenna coax cable connection). Refer to Radio Poor Reception. Radio Poor Reception
5. Other causes include defective relays, solenoids or switches. Refer to corrective action for additional tips on eliminating noise concerns.
Corrective Action
* Inspect the ground integrity of the component or system causing the noise.
* Malfunctioning and marginal components such as relays and solenoids may cause noise and/or poor reception.
* Always use a braided ground strap when applying additional grounds and keep the ground strap as short as possible. Total resistance of the braided ground strap should be 0.05 ohms or less.
* If the noise source is found to be coming from the vehicle harness:
- Route the antenna cable separately from the wire harness that is emitting the noise.
- Use aluminum or nickel tape in order to shield the antenna cable. Try variations of the following repairs:
* Try adding only aluminum or nickel tape before adding a ground strap to the tape.
* Wrap a ground strap 360 degrees around the tape, securing the other end of the strap to chassis ground.
Important: When installing suppression devices, signal wires such as sensor and communication circuits should not be suppressed. Battery and ignition voltage circuits are the best choices for suppressing.
* Capacitors work best on switch pops and low frequency noise.
* Filters work best on high frequency whines and static.
* After adding a suppression device, inspect all vehicle systems related or not related to the audio system for proper operation and function.
* Whenever possible, make a test harness that includes filters or capacitors. Always inspect the effectiveness and operation before permanent installation.
* If an audible pop is caused due to operating a switch, perform the following repairs as necessary:
- Add a capacitor across the contacts of the switch.
- If an audible pop is still present, add a capacitor from the battery positive voltage (B+) side of the switch to chassis ground.
- If an audible pop is still present, add a capacitor from the ground side of the switch to chassis ground.
Refer to the table for available noise suppression devices:
Generator Whine Concerns
1. Inspect the ground terminal and cable for high resistance.
2. Inspect the generator and brackets for loose or coated mounting bolts.
3. Inspect that the ground straps between the engine and the frame are clean and tight.
4. If the noise is still present, inspect the charging system for proper operation. Refer to Symptoms - Starting and Charging. Symptoms - Engine Electrical
5. Install filter GM P/N 1224205 in the battery voltage feed circuit to the radio.
6. If the noise is still present, install the filter in each of the following variations:
* Install the filter with the single wire side toward the radio and the ground wire attached to chassis ground.
* Remove the ground to the filter.
* Reverse the filter so the two wire side is toward the radio with the ground wire attached to chassis ground.
* Remove the ground from the filter.
7. If the installation of this filter causes a delay when turning the radio ON or OFF, or other noticeable performance problems, remove the filter and install a 0.47 micro farad capacitor (P/N 1227894) to chassis ground.
8. Before reassembling the vehicle, remove any unneeded filters.
9. Test the functionality of all the vehicle systems, including those not related to the audio system, for proper operation and function.