Traction control system? Have the dealer explain how the traction control system can make a noise when it is not active. The TC system is only active if it senses wheel slippage without brake pedal input.
If any wheel was slipping during a hard left, it would be the right, since the weight is all on the left. If the right wheel was slipping the TC will first reduce engine power (retard timing, shut off injectors) and as a last resort apply the right front brake.
I agree with Mike E, find another dealer. I don't remember hearing a sound like this in mine, but I'll try and remember to turn down the XM and listen tomorrow AM.
Do you have your foot on the brake pedal? Remember, the brake system is charged by a high-pressure accumulator and motor, and sometimes when you have applied the brakes the motor gears up to charge the accumulator. No weaselly vacuum assist for our H3s.
