Vehicle detects fault and displays message to service stability control system. specific problem not yet diagnosed. within a few moments, the display states that engine power is reduced. this causes a very unsafe condition as the vehicle slows to 10-15 mph. pressing gas pedal causes transmission to downshift to lower gear slowing vehicle further. cannot safely maneuver in traffic, brakes require much higher pedal pressure due to low vacuum boost after engine power reduced. insufficient warning that this is happening. problem is not with engine or powertrain, but engine power is cut (engine runs very rough as a result) in response to detected stability system error. engine runs fine if turned off and restarted. no overheating, oil level is fine, gasoline is good, no external problems. after restarting car drives fine initially, event recurs within 1 mile. very difficult to try to justify this kind of intentional vehicle control behavior. extremely poor design that causes an unsafe condition when a stability system error is detected.