I've never made that switch so I can't give advice on how to PM effectively (that probably is also very team- and project-dependent). But I imagine it might be a challenge to completely leave the engineer mindset behind. So I'd be careful to avoid talking with engineers as if you're still one of them, e.g. discussing technical challenges in depth, suggesting solutions, reviewing code. Stay focused on your new role as PM to avoid any confusion and keep the team humming along. Good luck!