Here is a code snippet to initialize the PWM module. It is not yet been tested since I had set that project aside for now. I hope it helps you get started.

You define the value of PTPER_VAL to set the PWM frequency. See table 17-2 of the PIC18F4431 datasheet for the suggested values.

Code:

;-----------------------------------------------------------
;   Init PWM module
;
         MOVLW    1<<PTMOD1       ; 1:1 prescale,1:1 postscale, up/down
         MOVWF    PTCON0
;
         MOVLW    1<<PWMEN2|1<<PWMEN1|1<<PMOD1|1<<PMOD0
         MOVWF    PWMCON0
;
         MOVLW    0               ; 1:1 Postscale
         MOVWF    PWMCON1
;
         MOVLW    LOW  PTPER_VAL
         MOVWF    PTPERL
         MOVLW    HIGH PTPER_VAL
         MOVWF    PTPERH
;
         CLRF     DTCON
;
         BSF      PTCON1,PTEN     ; Fire up the PWM module