Some owners of 2007-2010 GM passenger cars and trucks, Hummer H2/H3 and Saab 9-7X vehicles equipped with OnStar may complain about an audio whine coming from the radio speakers when using the OnStar system. The amplitude and frequency of the whine will change with an increase or decrease in engine speed
This condition may be caused by an electrical noise on the OnStar Vehicle Communication Interface Module (VCIM) battery feed wire being passed to the microphone output pins at the radio.
Technicians are to install a noise suppression filter, P/N 1224205 into the OnStar battery voltage circuit, a few inches from the VCIM. The filter package has three attached wires…a single yellow wire at one end with a yellow wire and a black wire at the other. Install the single yellow wire side into the battery voltage circuit towards the VCIM. Install the remaining single yellow wire into the battery voltage circuit toward the fuse and the black wire to ground.
Important: The noise suppression filter is polarity sensitive. The filter is designed to be most effective when the end with the capacitor ground is connected towards the source of the electrical noise. Install the filter in this polarity first. If the noise level is still not satisfactory, try disconnecting the capacitor ground. In some cases, if the first installation does not correct the noise issue, try reversing the filter polarity (remove the filter, turn it end-for-end and reinstall) and ground the capacitor lead.