The voltage regulator is in the alternator. I'm assuming you replaced it
with an OEM alternator? Don't use an AutoZone one. They are just rebuilds
and fail quite a bit. Often they just replace the brushes and nothing else.
The ECU is throwing a code because it isn't getting the voltage it wants.
You should follow the step on page 13A-196 of the manual.

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Todd Honea
> The car gave a engine code 1500(Generator FR terminal circuit
> malfunction).I not sure what that means. I have the manual but it does
> give any specific definition for code. I replaced the alternator and
> battery. The car runs for a while and then the power drains out.Is it the
> voltage regulator? What is the solution for the code 1500?