general problems of the 2000 Lexus GS400

While driving on the highway my car suddenly stop with no apparent reason at all. I tried to accelerate but it did not responded, eventhough the engine was running perfectly. Everything was working but the accelerator. When taken to the Lexus dealer they told me the problem was with the electronic control module. They told me it will cost me around $3,000. 00 to replace it. Is this normal for this car to happen or is it normal wear and tear?. We did not have an accident because it was early in the morning but it could be worse during heavy traffic hours.