ADCON1 = %00000000
FVRCON = %11000010 'voltage reference set to 2.048V
you are setting the frv (ps bit 6 of fvrcon is read only) but never connecting it to the adc module .
to use the fvr as ref you need to set adcon1 bits 0 & 1 to 1

you have also selected a conversion clock of fosc/2 which @4mhz is out of specs
you need fosc/4 or rc clock for adc