Help with BIOS Disk Read Interrupt

[Mr. Mysterio]

I've been trying to write a MBR that bootstraps code from the disk. I've been trying to use the BIOS interrupt 0x13 with ah=2, but it always fills the memory with zeros. The return is ah = 0 = success, and al = the correct number of read sectors. I'm using NASM. Here is my code:

[org 0x7c00]
[BITS 16]
 
; Init stack.
mov bp, 0x7B00
mov sp, bp
 
mov ah , 0x02 ; BIOS read sector function.
mov al , 0x01 ; Read 1 sector.
mov ch , 0x00 ; Cylinder 0.
mov dh , 0x00 ; Head 0.
mov cl , 0x02 ; Start from sector 2.
mov bx, 0
mov es, bx
mov bx, 0x8000 ; Read data to 0x0000:0x8000. dl already contains the boot drive index.
int 0x13
jc disk_error ; Jump if error.
 
mov bx, 0x8000 ; Start from 0x8000.
mov ax, 0x200 ; Read 512 bytes.
clc ; Do not prepend "0x".
call printx ; Print bytes as hex.
 
jmp $

I've tried starting from sectors 0 through 5 and reading different amounts with no luck. I haven't been using an emulator, I've been directly testing it on a PC. I had this function working once in the past so I know it can work with my SD card, but my HDD died and killed that data. I haven't been able to get it working again. Please help!