brandnewyc

Anybody have this problem on there Cobalt SS when I listen to the XM radio I hear a whine in my speakers only when the car is on. I took it the dealer they said they found out what is causing the whine, fuel pump but GM will not fix it since it only affects the XM radio. Does anybody else have this problem? It’s been making the whine since I bought the car and has been gradually getting worse had it for 3 Months. I have been talking to Chevy Customer support to get it fix but they keep calling me when I am work and can’t answer. EMI is Electromagnetic Interference and also called RFI (Radio Frequency interference)

Stamina

That's wierd that it's only happening on XM. XM is a digital format, so you're either going to hear the music clearly or not at all, and you shouldn't hear any EMI sound (as far as receiving the signal). Keeping that in mind, they may have installed a noise filter on the AM/FM radio input circuits but not the XM one since they figured it wouldn't be needed. Are you sure you're not hearing the noise on AM/FM too?

The EMI may be wirelessly interacting with your radio or speakers, similar to how TDMA (AT&T/Cingular and T-Mobile) phones cause wierd sounds to happen when the phone is near a radio, speaker, or microphone. Another possibility is that the fuel pump or whatever else it might be is causing the noise to distribute over the power system in the car, in which case adding a noise filter between the power source and radio could help isolate it.

Iam Broke

iTrader: (10)

If the EMI varies with engine RPM, it's coming from the alternator. Common in older cars. Could be a bad diode or filter cap.
If it's a constant pitch, then I could believe the electric fuel pump, or heater blower motor if it changes freq with a change in fan speed.

silver187666

my car did that when i had the ipod transmiter

BartSS

You don't have subs in that car do u? Cus if the power wire and the rcas are ran on the same side you would hear it too

brandnewyc

Yeah it does not do it on am/fm but the xm reciever recieves the digital signal then converts it to analog sound and then to the headunit radio.

Yeah I have the stock sub but the noise is only there if the car on or take out the fuel pump fuse and it goes away. IDK what is wrong I never messed with my car radio.

It is a constant pitch and it goes away when i take out the fuse for the fuel pump.

Do you guys think it is a defective fuel pump? The dealership replaced the xm reciever but say GM will not change the fuel pump..

StreetDreamz

You are experiencing a difference in potential between two ground points of the radio and XM tuner with the fuel pump grounding to or in between the radio ground and XM tuner ground path. Find a wiring schematic for the XM tuner section and find the dedicated ground wire/point. Try extending the ground wire and run it to the radio ground physically or grounding the XM unit closer to the unit itself, instead of tied in with a bunch of other grounds. This, in theory, will most likely create a higher potential difference than before, but it may eliminate the fuel pump ground interference. It is my understanding that while the XM tuner sends its information digitally to the radio, its audio signal is still analog with a low impedance, low voltage shielded, possibly common return path between left and right signal. It is possible that the power supply for the fuel pump is ran in the same bundle as the XM tuner signal wires and is causing an EMI. Does it come from both left and right channels or just one? The XM signal wiring could have a break in the insulation, allowing the fuel pump feed to bleed into the audio signal from the XM tuner. It is also possible that there is a bad filter in the stock radio because the XM tuner is patched in as an auxiliary source and therefore needs to have seperate circuits to decode the information and relay it to the radio controls/outputs. Granted this is all digitally data driven, audio output is still analog in its purest form and will always be. Old school tip of the day: Take a bunch of bare copper wire and wind it tightly around the audio signal outputs of the XM tuner and ground it. If your noise goes away then you have EMI, most likely from the fuel pump power feed.

-Christopher Dembowski
MECP Certified Master Installer
CN# CEA172211