For anyone wanting to get their own access to the engineering menu in an SE, I'll just leave this here.
Entered_Serial_Number is your cars serial number.
JavaScript:
public static String getPassword(String Entered_Serial_Number) {
BigInteger bigInteger = new BigInteger(HMacMD5.getHmacMd5Str(Entered_Serial_number, new SimpleDateFormat("yyMMdd").format(new Date())).substring(0, 8), 16);
return SHA256Util.getSHA256Str((bigInteger.longValue() + "").substring(0, 8));
}
edit: edited down to the basic function and removed all the extra checks and trims.