diff --git a/data/ui.js b/data/ui.js
index 84033fb..aca1a62 100644
--- a/data/ui.js
+++ b/data/ui.js
@@ -29,9 +29,11 @@ var ui = {
 	// temp variable to store updates from Parameter Database
 	paramUpdates: "",
 
-	// Status of visibility of parameter categories. E.g. Motor, Inverter. true = visible, false = not visible.
+  // Status of visibility of parameter categories. E.g. Motor, Inverter. true = visible, false = not visible.
 	categoryVisible: {},
 
+	canMappingLoaded: false,
+
 	navbarIsBig: true,
 
 	// When true, fetch all parameters including hidden ones (via 'json hidden')
@@ -177,7 +179,6 @@ var ui = {
 		ui.updateTables();
 		plot.generateChart();
 		ui.parameterDatabaseCheckForUpdates();
-		inverter.canMapping(ui.populateExistingCanMappingTable);
 		wifi.populateWiFiTab();
 		settings.populateSettingsTab();
 		ui.populateFileList();
@@ -366,6 +367,10 @@ var ui = {
 			}
       ui.populateVersion();
       ui.populateSpotValueDropDown();
+      if (!ui.canMappingLoaded && Object.keys(values).length > 0) {
+        ui.canMappingLoaded = true;
+        inverter.canMapping(ui.populateExistingCanMappingTable);
+      }
 
 			document.getElementById("paramDownload").href = "data:text/json;charset=utf-8," + encodeURIComponent(JSON.stringify(params, null, 2));
 			document.getElementById("spinner-div").style.visibility = "hidden";
diff --git a/esp32-web-interface.ino b/esp32-web-interface.ino
index 1e2eabf..91f9889 100644
--- a/esp32-web-interface.ino
+++ b/esp32-web-interface.ino
@@ -611,8 +611,10 @@ static void handleCanMap() {
       res = OICan::AddCanMapping(server.arg("edit"));
   }
 
-  if (res == OICan::Ok)
-    OICan::SendCanMapping(server.client());
+  if (res == OICan::Ok) {
+    if (!OICan::SendCanMapping(server.client()))
+      server.send(500, "text/plain", "CAN communication error");
+  }
   else if (res == OICan::CommError)
     server.send(500, "text/plain", "CAN communication error");
   else if (res == OICan::UnknownIndex)
diff --git a/src/oi_can.cpp b/src/oi_can.cpp
index 822b8e1..22a09ee 100644
--- a/src/oi_can.cpp
+++ b/src/oi_can.cpp
@@ -58,9 +58,9 @@
 #define SDO_CMD_LOAD          1
 #define SDO_CMD_RESET         2
 #define SDO_CMD_DEFAULTS      3
-#define SDO_CMD_CLEAR_CAN     4
 #define SDO_CMD_START         4
 #define SDO_CMD_STOP          5
+#define SDO_CMD_CLEAR_CAN     6
 #define PARAM_FLAG_HIDDEN     1
 #define MAX_ERROR_LOG_ENTRIES 100
 
@@ -404,7 +404,12 @@ bool SendJson(WiFiClient client, bool includeHidden) {
   return failed < 5;
 }
 
-void SendCanMapping(WiFiClient client) {
+bool SendCanMapping(WiFiClient client) {
+  if (state != IDLE || updstate != UPD_IDLE) {
+    DBG_OUTPUT_PORT.printf("SendCanMapping rejected: CAN state=%d update state=%d\r\n", state, updstate);
+    return false;
+  }
+
   enum ReqMapStt { START, COBID, DATAPOSLEN, GAINOFS, DONE };
 
   twai_message_t rxframe;
@@ -509,6 +514,7 @@ void SendCanMapping(WiFiClient client) {
 
   WriteBufferingStream bufferedWifiClient{client, 1000};
   serializeJson(doc, bufferedWifiClient);
+  return true;
 }
 
 SetResult AddCanMapping(String json) {
@@ -916,9 +922,9 @@ void Loop() {
 
     retries--;
 
-    if (recvdResponse || retries < 0)
+    if (state == IDLE || state == OBTAIN_JSON || retries < 0)
       updstate = UPD_IDLE; //if request was successful
-    else
+    else if (!recvdResponse)
       requestSdoElement(SDO_INDEX_SERIAL, 0);
 
      delay(100);