Hummer H2. Manual - part 273

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Check for any aftermarket equipment that may have been installed on the vehicle. If aftermarket 
equipment is found disconnect it and check if the audio noise is still present. 

Inspect that the antenna connector and the antenna coaxial cable are clean and tight. 

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For reception concerns, first determine if the customer is within the listening area of the stations they are 
attempting to receive.  

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Stations at the lower end of the FM band are more susceptible to audio noises than stations at the higher 
end.  

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If the noise is only from one speaker check for the following before speaker replacement: 

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Isolate the noise using the J 39916-A CD and Cassette Diagnostic Audio Kit. See Special Tools 
and Equipment .  

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Inspect the speaker connections to ensure they are clean and tight. Refer to Testing for 
Intermittent Conditions and Poor Connections in Wiring Systems.  

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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.  

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Ignition noise on the FM band may be an indication of an ignition system problem.  

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Inspect that all vehicle grounds are clean, tight and free of corrosion.  

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Inspect the rear defogger grid lines for large breaks or dark spots.  

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Inspect the connections at the radio antenna module if equipped, to ensure that they are clean and tight.  

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Compare the customers vehicle to another of similar model and audio system to determine if the 
condition is abnormal.  

Identifying Concerns 

1. 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 88-108 FM then 550-1600 AM.  

4. Record the number of valid radio stations where the tuner stops.  

5. Repeat these steps with the ignition ON, and the engine OFF then again with the engine running.  

2. Return the ignition switch to the position that the concern was most noticeable.  

3. Remove fuses or circuit breakers one at a time until the noise has been eliminated.  

4. Identify what systems or components are powered by the fuse.  

5. Reinstall all fuses and circuit breakers.  

6. Disconnect the components powered by the fuse one at a time until the concern has been eliminated.  

Corrective Action 

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Inspect the ground integrity of the component or system causing the noise. 

 

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Malfunctioning and marginal components such as relays and solenoids may cause noise and/or poor 
reception.  

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Always use a braided ground strap when applying additional grounds and keep the ground strap as short 
as possible.  

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If the noise source is found to be coming from the vehicle harness: 

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Route the antenna cable separately from the wire harness that is emitting the noise.  

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Use aluminum or nickel tape in order to shield the antenna cable. Try variations of the following 
repairs: 

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Try adding only aluminum or nickel tape before adding a ground strap to the tape.  

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Wrap a ground strap 360 degrees around the tape, securing the other end of the strap to 
chassis ground.  

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Capacitors work best on switch pops and low frequency noise.  

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Filters work best on high frequency whines and static.  

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After adding any suppression device, inspect all of the vehicle systems including those not related to the 
audio system, for proper operation and function.  

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Whenever possible, make a test harness that includes filters or capacitors. Always inspect the 
effectiveness and operation before permanent installation.  

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If an audible pop is caused due to operating a switch, perform the following repairs as necessary: 

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Add a capacitor across the contacts of the switch.  

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Add a capacitor from the battery positive voltage (B+) side of the switch to chassis ground.  

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Add a capacitor from the ground side of the switch to chassis ground.  

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Use the following available noise suppression devices: 

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220 micro farad (50 V) capacitor GM P/N 1227895 - Works well for ignition system related noise.  

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0.47 micro farad capacitor GM P/N 1227894 - Works well for switches and relays.  

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Feed through capacitor GM P/N 477371 - Works well for high current situations.  

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Filter package GM P/N 1224205 - Works well for low current situations.  

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Fuel pump suppressor GM P/N 25027405  

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21 inch braided ground strap GM P/N 8910791  

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19 inch braided ground strap GM P/N 6286800  

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10.5 inch braided ground strap GM P/N 6287160  

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8.5 inch braided ground strap GM P/N 12091511  

Generator Whine Concerns 

1. Inspect the ground terminal and cable for high resistance. 

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.

 

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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 Diagnostic Starting 

Point - Engine Electrical in Engine Electrical.  

5. Install a filter GM P/N 1224205 in the battery voltage feed circuit to the radio.  

6. If the noise is not eliminated, install the filter in each following variation: 

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Install the filter with the single wire side toward the radio and the ground wire attached to chassis 
ground.  

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Remove the ground to the filter.  

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Reverse the filter so the 2-wire side is toward the radio with the ground wire attached to chassis 
ground.  

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Remove the ground from the filter.  

7. If the filter GM P/N 1224205 causes a delay when turning the radio ON or OFF, or other problems, 

remove the filter and install a 0.47 micro farad capacitor to chassis ground.  

8. Before reassembling the vehicle, remove any unneeded filters.  

9. Test the functionality all of the vehicle systems including those not related to the audio system, for proper 

operation and function.  

RADIO POOR RECEPTION 

Schematic Reference: Radio/Audio System Schematics (non Class 2 Amplifier) or Radio/Audio System 
Schematics (Class 2 Amplifier) 

Diagnostic System Check - Entertainment System 

Always perform the Radio/Audio System Diagnostic System Check before proceeding with these diagnostic 
procedures. Refer to Diagnostic System Check - Entertainment System . 

Antenna System Test 

1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure 

(Single Battery) in Engine Electrical.  

2. Disconnect the antenna lead-in connector from the radio receiver.  

3. Measure the resistance from the negative battery cable to the coax outer conductor connector.  

4. The resistance measured should be 0.20 ohm or less.  

5. Test the following when the resistance is greater than 0.20 ohm. 

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Base of the antenna for a poor connection to body ground.  

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The coaxial cable interconnects for a poor connection or corrosion.  

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Test for an open or high resistance from the battery negative cable to the body. Refer to Circuit 

IMPORTANT: Always zero out the DMM before taking a resistance measurement in order to 

ensure an accurate reading.

 

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Testing and Wiring Repairs in Wiring Systems. 

6. After finding and correcting the condition, operate the system in order to verify the repair.  

Perform the Antenna Checking Procedures after confirming the integrity of the antenna ground. 

Antenna Checking Procedures 

Perform the following tests for the type of antenna on the vehicle. 

Mast Antennas 

Unplug antenna lead-in connector from radio receiver and plug a test antenna into radio. Make sure antenna 
base is grounded to the vehicle chassis and keep hands off the mast. 

Check radio reception in an area away from electrical interferences. Tune to several weak and strong AM and 
FM stations. If the radio reception improved, the problem exists with the antenna and/or lead-in cable. If the 
reception is still poor, refer to Audio System Troubleshooting Hints . 

Fig. 12: Mast Antenna System 
Courtesy of GENERAL MOTORS CORP.

IMPORTANT: Always zero out the DMM before taking a resistance measurement in order to 

ensure an accurate reading.

 

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