Increase volts at OBD port

Make sure you have battery voltage on pin 16, and ground at 4. If you have voltage, probably have scanner problems.

Check for corrosion or discolored pins on the tester and receptacle. Your tester could have bad connection internally causing it to “see” a low voltage from your vehicle. If you have a multimeter check for the correct voltage at the test receptacle. If that’s not where it should be, I would trace the wiring looking for a resistance (ie, corrosion or loose connection) that shouldn’t be there. You may have pinched a wire when you installed the new engine. I hope this helps, Good luck!

I have 35 years experience doing electrical and avionics work on military jet aircraft to base my thoughts on.