Intermittent Pop/Thump Noise From Left Front Radio Speaker When Starting Vehicle (Normal Characteristic of Vehicle)
| Subject: | Intermittent Pop/Thump Noise From Left Front Radio Speaker When Starting Vehicle (Normal Characteristic Of Vehicle) |
| Models: | 2005-2007 Buick Rainier |
| 2005-2008 Chevrolet TrailBlazer Models |
| 2005-2008 GMC Envoy Models |
| with Navigation Radio (RPO UM8) |
This bulletin is being revised to add the 2008 model year. Please discard Corporate Bulletin Number 06-08-44-021 (Section 08 -- Body and Accessories).
Condition
Some customers may comment on an intermittent pop or thump type noise from the left front speaker when the vehicle is started.
Cause
This condition may occur if the chimes are active prior to attempting to start the engine (door open or seat belt not fastened). When the vehicle is started, a thump noise may be heard from the left front speaker.
Correction
Do This | Don't Do This |
|---|---|
This is a normal characteristic of the vehicle. No repairs are necessary. | Do not replace the navigation radio, amplifier or attempt any repairs on the related systems or wiring. |
The vehicle will not exhibit this condition if it is started rapidly with no pause from the Off to the crank position and the doors are closed with the seat belt fastened (so that the chimes are not active when starting). The thump noise is a characteristic of the Navigation Radio system analog processor. This architecture has a regulated 8.5 volt supply in the mixer circuit to bring in the "voice prompt signal" and the "chime" signal to a common audio output. When the regulated voltage output dips, a transient on the audio output may lead to the thump noise.
