An ethical Project Manager is a successful Project Manager. The PMI has established a Professional Code of Ethics that all Project Management Professionals (PMP) must adhere to. These ethics are meant to ensure that all PMPs abide by a set of values, and they live up to those values in pursuit of their careers.
Project Ethics won't ensure you are a successful project manager, however not behaving ethically will almost always ensure your project will fail. As stated in the PMI Code of conduct, which in my opinion is the most important ethical behavior, a project manager must accept responsibility for his or her actions. This means admitting to all your stakeholders when you are wrong, learning from your mistakes, and putting actions into place that will help you to avoid making the same mistake twice.
A project manager is responsible for all activities that occur or fail to occur on their project. It is unethical for a project manager to blame others for mistakes that were clearly the fault of the project manager.
Do you have the ethics to accept and take responsibility for your mistakes? Are you willing to do this in the face of your harshest critics? If not, you need to leave the project management profession because you aren’t a mature, responsible professional, and as such you are hurting the profession of Project Management.