Index: dialin/ui/hd_simulator.py
===================================================================
diff -u -r2abf398a7fffa390c46f8d41403de44575ffd97e -rda62b4e5e9f194570c53346691dd8959272f740d
--- dialin/ui/hd_simulator.py	(.../hd_simulator.py)	(revision 2abf398a7fffa390c46f8d41403de44575ffd97e)
+++ dialin/ui/hd_simulator.py	(.../hd_simulator.py)	(revision da62b4e5e9f194570c53346691dd8959272f740d)
@@ -2166,3 +2166,19 @@
                                               payload=payload)
 
         self.can_interface.send(message, 0)
+
+    def cmd_send_hd_service_mode_response(self, accepted: int, reason: int) -> None:
+        """
+        A simulated HD response message of service mode request
+        @param accepted: (int) acceptance. 1 if accepted
+        @param reason: (int) rejection reason
+        @return: None
+        """
+        payload = unsigned_integer_to_bytearray(accepted)
+        payload += unsigned_integer_to_bytearray(reason)
+
+        message = DenaliMessage.build_message(channel_id=DenaliChannels.hd_to_ui_ch_id,
+                                              message_id=MsgIds.MSG_ID_HD_RESPONSE_SERVICE_MODE_REQUEST.value,
+                                              payload=payload)
+
+        self.can_interface.send(message, 0)
\ No newline at end of file