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I've found info that the valves are controlled via pulse width modulation generated by the chassis control module. See the attached diagram.
My car starts up loud even in snow/ice mode for the first few seconds. Also the vehicle menu is not available unless the car is running. Pushing the start button once or twice without a foot on the brake doesn't enable the menu either. The only way I've found is to put the car in stealth mode before shutting it off. So far, I'm not real good at remembering that.
A lengthy description of how it works:
Exhaust Tailpipe Flow Control Valve System
The exhaust tailpipe flow control system is used to tune the exhaust
note for high performance vehicles. The vehicle is equipped with two
tailpipe exhaust valves. One in the left tailpipe and one in the right
tailpipe. Each exhaust tailpipe valve is installed in the low
restriction exhaust path of a dual outlet muffler, near the exhaust tip.
When a tailpipe exhaust valve is open, the low restriction exhaust
path is opened to the atmosphere, and the exhaust note becomes more aggressive.
An output circuit from the chassis control module is used to control the
actuator that opens the left and right exhaust tailpipe valves. The
exhaust flow control valve opens and closes when the chassis control
module commands the actuator by pulse width modulation of the control signal.
To provide a more aggressive exhaust note when the vehicle is started,
the exhaust tailpipe valves are opened during an engine crank event
during specific modes of operation if that option is available. Once
the engine is running, accelerator pedal position, transmission gear
and engine speed are used to determine the commanded state (open or closed)
of the exhaust tailpipe valves.
There are four specific exhaust performance modes that result in different
behavior of the exhaust tailpipe valves. These modes are:
Note: You may notice an exhaust tone change due to the AFM system activation,
or during certain driving conditions to meet Federal noise pass-by regulations.
Review the cylinder deactivation exhaust flow control system operational
modes listed below for additional details.
Winter/Eco Mode: Exhaust tailpipe valves will be closed at all times when
the engine is running.
Tour Mode: Exhaust tailpipe valves are closed when the engine is idling and
during normal/non-aggressive driving. Valves open during aggressive driving.
Sport Mode: Exhaust tailpipe valves are open when the engine is idling and
during most driving scenarios. See note above.
Track Mode: Exhaust tailpipe valves are open at all times. See note above.
It is possible to personalize the exhaust sound. When engine sound
enhancement is turned off via the personalization menu, the exhaust
tailpipe valves will be put into track mode no matter which vehicle
mode (Winter/Eco, Tour, Sport, or Track) is displayed on the drivers
instrument panel.
I don't know if putting a constant 12vdc signal to the control valve will close it or cause the module to fail (ie burn up). There is a calibration procedure if the valve module is replaced, implying that it is not an on/off type of valve.......the programming could have "partial open at xx%" modes while driving.
I'd like to see if it works, but don't want to burn up the module/controller.
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