Can you be a successful Project Manager without functional and technical knowledge of the delivery?

The main purpose of this article is to invoke a debate on the topic of what constitutes a successful project manager and can success be achieved by following some project management procedures without having functional or technical knowledge of the work that the team is doing.

Personally speaking, I find success difficult to achieve if my knowledge of the subject/product/project is incomplete. I have always struggled to complete my deliverables if I don't know what the overall picture is.

Processes that have helped me achieve an average work till I learned, are from my knowledge of PMP and PMI-ACP from PMI and Agile methodologies. The process defined by PMI and the company standards help a person to streamline and execute deliveries. All of the work would mostly be on time and would achieve a degree of client success.

But once you will learn the technology/functionality behind the process/product you can achieve excellence.

The one aspect in which this learning helps is that it creates a bridge between the project manager and the team doing the work. The team now understands that the PM not only follows a process but is capable of understanding exactly what they are working on and the challenges faced during that work and hence empathize with them and clearly represent them in front of the customer.

The other good point in learning is that you also can help the team and customers in thinking beyond the box.

I leave you with this thought and let me know what you think. Will only the processes be enough? If yes, then why are all PMs not successful.