P1246 I replace several alternators, new.

P1246 - Alternator Load Input Failed

Possible causes†GEN-MON circuit short to GND.
GEN-MON circuit short to B+.
GEN-MON circuit open.
GEN-COM circuit short to GND.
GEN-COM circuit short to B+.
GEN-COM circuit open.
ILC circuit short to GND.
ILC circuit short to B+.
ILC circuit open.
Battery-sense circuit open.
Generator drive mechanism.
Damaged generator/regulator assembly.
Damaged PCM.

P1246 Description:
The PCM monitors generator load from the generator/regulator in the form of frequency. The frequency range is determined by the temperature of the voltage regulator, where 97% indicates full load, and below 6% indicates no load.

Verify the battery voltage is 14.5 volts.
Verify the generator/regulator has the correct part number.

I did find a TSB about this issue for the 2000-2001 but not on the 2002 model year it is possible you may actually have a 2001 but made mid year and classified as a 2002
Could you please provide me with the build date ( MO/YR) from the drivers door sticker.

There was, a TSB about replacing wire harnes's used on these vehicles, however no recall. A PCM reflash probably wasnt neccesary, as it may actually be causing the issue.

If you have replaced this a few time where are the parts comming from? If you can get part numbers throw them in the post here. If there salvage that maybe the correct tree we need to bark up so to speak.

Sorry for the late reply, the original post was supposed to be 13.5 volts. Typo on my part. Has the PCM been looked into these are known for causing a no charge condition were it does not cycle the alt like it should

If it is indeed charging the battery like it should. Then the issue is a wiring problem behind the dash somewhere causing the battery light to come on.