diff --git a/src/constants.ts b/src/constants.ts
index 2dff4dabc..1e7176339 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -89,6 +89,10 @@ export const CONSTANTS = {
       "error.noPythonPath",
       "We found that you don't have Python 3 installed on your computer, please install the latest version, add it to your PATH and try again."
     ),
+    RECONNECT_DEVICE: localize(
+      "error.reconnectDevice",
+      "Please disconnect your Circuit Playground Express and try again."
+    ),
     STDERR: (data: string) => {
       return localize("error.stderr", `\n[ERROR] ${data} \n`);
     },
@@ -204,6 +208,10 @@ export const CONSTANTS = {
     SERIAL_MONITOR_NAME: localize(
       "misc.serialMonitorName",
       "Pacifica Serial Monitor"
+    ),
+    SERIAL_MONITOR_TEST_IF_OPEN: localize(
+      "misc.testIfPortOpen",
+      "Test if serial port is open"
     )
   },
   NAME: localize("name", "Pacifica Simulator"),
diff --git a/src/serialPortControl.ts b/src/serialPortControl.ts
index b34bf9350..0b3eb3912 100644
--- a/src/serialPortControl.ts
+++ b/src/serialPortControl.ts
@@ -73,9 +73,10 @@ export class SerialPortControl {
                 this._currentSerialPort = new SerialPortControl.serialport(this._currentPort, { baudRate: this._currentBaudRate });
                 this._outputChannel.show();
                 this._currentSerialPort.on("open", () => {
-                    this._currentSerialPort.write("msft", "Both NL & CR", (err: any) => {
+                    this._currentSerialPort.write(CONSTANTS.MISC.SERIAL_MONITOR_TEST_IF_OPEN, "Both NL & CR", (err: any) => {
                         if (err && !(err.message.indexOf(CONSTANTS.ERROR.COMPORT_UNKNOWN_ERROR) >= 0)) {
                             logToOutputChannel(this._outputChannel, CONSTANTS.ERROR.FAILED_TO_OPEN_SERIAL_PORT(this._currentPort));
+                            logToOutputChannel(this._outputChannel, CONSTANTS.ERROR.RECONNECT_DEVICE);
                             reject(err);
                         } else {
                             logToOutputChannel(this._outputChannel, CONSTANTS.INFO.OPENED_SERIAL_PORT(this._currentPort));