Index: firmware/App/Services/SystemCommMessages.c
===================================================================
diff -u -r7dae221794a30c403c06d90e12f3ab28830dffbe -r8c195e4b22d63a6b8de9089ff6bf704282f54885
--- firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 7dae221794a30c403c06d90e12f3ab28830dffbe)
+++ firmware/App/Services/SystemCommMessages.c	(.../SystemCommMessages.c)	(revision 8c195e4b22d63a6b8de9089ff6bf704282f54885)
@@ -997,12 +997,12 @@
  *************************************************************************/
 void handleChemDisinfectUIStateReadingFromDG( MESSAGE_T *message )
 {
-    if ( message->hdr.payloadLen == sizeof(MODE_CHEMICAL_DISINFECT_DATA_T) )
+    if ( message->hdr.payloadLen == sizeof( MODE_CHEMICAL_DISINFECT_DATA_T ) )
     {
         MODE_CHEMICAL_DISINFECT_DATA_T payload;
         DG_DISINFECT_UI_STATES_T uiStates;
 
-        memcpy( &payload, message->payload, sizeof(MODE_CHEMICAL_DISINFECT_DATA_T) );
+        memcpy( &payload, message->payload, sizeof( MODE_CHEMICAL_DISINFECT_DATA_T ) );
 
         uiStates.heatDisinfectUIState = 0;
         uiStates.chemDisinfectUIState = payload.chemDisinfectUIState;
@@ -2009,7 +2009,15 @@
  *************************************************************************/
 void handleDGCheckIn( MESSAGE_T *message )
 {
-    checkInFromDG();
+    if ( message->hdr.payloadLen == sizeof( U32 ) )
+    {
+        checkInFromDG();
+    }
+
+    else
+    {
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_DG, FALSE );
+    }
 }
 
 /*********************************************************************//**
@@ -2022,7 +2030,16 @@
  *************************************************************************/
 void handleUICheckIn( MESSAGE_T *message )
 {
-    checkInFromUI();
+
+    if ( message->hdr.payloadLen == 0 )
+    {
+        checkInFromUI();
+    }
+
+    else
+    {
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, FALSE );
+    }
 }
 
 /*********************************************************************//**
@@ -2103,7 +2120,7 @@
     }
     else
     {
-        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, FALSE );
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, ACK_NOT_REQUIRED );
     }
 }
 
@@ -2131,7 +2148,7 @@
     }
     else
     {
-        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, FALSE );
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, ACK_NOT_REQUIRED );
     }
 }
 
@@ -2162,7 +2179,7 @@
     memcpy( payloadPtr, &testID, sizeof( U32) );
 
     // Serialize the message (w/ sync, CRC, and appropriate CAN padding) and add serialized message data to appropriate comm buffer
-    result = serializeMessage( msg, COMM_BUFFER_OUT_CAN_HD_BROADCAST, ACK_NOT_REQUIRED ); // TODO - make ack required when UI ready
+    result = serializeMessage( msg, COMM_BUFFER_OUT_CAN_HD_BROADCAST, ACK_REQUIRED );
 
     return result;
 
@@ -2216,7 +2233,7 @@
     }
     else
     {
-        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, FALSE );
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, ACK_NOT_REQUIRED );
     }
 }
 
@@ -2266,7 +2283,7 @@
     }
     else
     {
-        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, FALSE );
+        sendAckResponseMsg( (MSG_ID_T)message->hdr.msgID, COMM_BUFFER_OUT_CAN_HD_2_UI, ACK_NOT_REQUIRED );
     }
 }