The project manager is assigned to get the promised deliverable on time. A good project manager will also ensure the deliverable is of the best quality possible without further delaying the project and without asking the team members to put in more resources than the project plan!
Since your project manager wears the 'Developer's hat' too, and I am guessing (in your company) He (the project manager) has a long experience being a developer then rose up to the rank/position of the project manager, so he is an experienced developer as well. If that's how he rose up to the rank in your company and thats how your company interprets 'project manager' too then you be fine running your code through him. It doesn't suggest that you lack confidence in your code, rather suggests that you don't hesitate to ask questions even on your own work in pursuit of a higher quality deliverable. Also, research about the logic blocks you are coding and see what are other practices over the internet. During the code review, suggest those different practices to your 'project manager' to show that you are well aware of how else it could be done, just didn't know what would best suit your organization in the longer run. This will suggest that you have a wide perspective and can think out of the box to find the best route to the solution. A good skill for a programmer.
But usually (by PMI conventions) a project manager is a temporary position that a fellow takes up for the term of the project and he is given the hat to manage the project, not necessarily to make sure that the deliverable are of the utmost quality. There are other people to take care of that, even peers of the developers.