Morning,

Wondering if anyone can assist.

I redid the engine in my car and coded the keys. The issue now is that all it does it swing but does not start.
The dash indicates a light that shows a missing key.

Any help will be appreciated.

 

It would seem that you didn't actually code the keys to the vehicle. Never done this before, but if it's got a missing key light on the dash, I would take that as it's not detecting the key(s).

 

Ditto. I'm thinking the exact same thing.

 

First, I'm not certain what you mean by "redid my engine".
If you mean pulled your engine and rebuilt/replaced it that could mean multiple electrical connection issues.

As for the light there are multiple reason for this.
Incorrect programming (do you have the correct scan tools to identify the error codes and program your FOBs and did you follow the correct procedure)
Bad vehicle battery (have you had your battery load tested)
Bad FOB battery (did you put new batteries in your FOBs)
FOB not communicating with anti-theft system (incorrect programming and/or electrical issues)
Or it could be a combination of any of the above.

You can attempt to spend the time and headaches to find the issue(s) or take it to someone who is qualified to do so.
That is your call; it won't be inexpensive, but it will be fixed correctly.

 

I always look where a 'new" member resides before making any advice. In this case it would be to the 1 of only 2 Mazda dealerships to go to correct the issue of no start and no communication between the vehicle and its fobs. I casually looked in the area that the new members country listed and did not find any certified auto service centers so going to anything, but a Mazda dealership may be inadvisable.

If the key fobs worked before the service of the engine whatever that may have been then something was done incorrectly or overlooked when finishing the service of the engine. If the reprograming of the fobs was not done exactly by the correct "how- to" then you would have lost communication to both fobs. If that happened, then a professional that has the proper tools and experience would likely need to reset the fob and other onboard electronics? There also may be a slim chase that the ECU will need a flash?