diff --git a/loop/SARA_send_data_v2.py b/loop/SARA_send_data_v2.py
index 4e7c135..98d768b 100755
--- a/loop/SARA_send_data_v2.py
+++ b/loop/SARA_send_data_v2.py
@@ -847,9 +847,17 @@ try:
     payload_csv[19] = npm_hum
 
     # npm_status: last value only (no average), use rowid (not timestamp)
-    npm_status_value = rows[0][7] if rows and rows[0][7] is not None else 0
-    payload.set_npm_status(npm_status_value)
-    print(f"NPM status: 0x{npm_status_value:02X}")
+    npm_status_value = rows[0][7] if rows and rows[0][7] is not None else 0xFF
+
+    npm_disconnected = False
+    if npm_status_value == 0xFF:
+        # 0xFF = NPM disconnected/no response → will set ERR_NPM in error_flags
+        npm_disconnected = True
+        print("NPM status: 0xFF (disconnected)")
+    else:
+        # Valid status from NPM → send as byte 67
+        payload.set_npm_status(npm_status_value)
+        print(f"NPM status: 0x{npm_status_value:02X}")
 
     #add data to payload UDP
     payload.set_npm_core(PM1, PM25, PM10)
@@ -1139,6 +1147,8 @@ try:
         error_flags |= ERR_RTC_DISCONNECTED
     if rtc_status == "reset":
         error_flags |= ERR_RTC_RESET
+    if npm_disconnected:
+        error_flags |= ERR_NPM
     payload.set_error_flags(error_flags)
 
     # ---- Firmware version (bytes 69-71) ----