diff --git a/localization/ekf_localizer/config/ekf_localizer.param.yaml b/localization/ekf_localizer/config/ekf_localizer.param.yaml
index 667217d2591dc..1c16624605907 100644
--- a/localization/ekf_localizer/config/ekf_localizer.param.yaml
+++ b/localization/ekf_localizer/config/ekf_localizer.param.yaml
@@ -24,9 +24,9 @@
 
     # for diagnostics
     pose_no_update_count_threshold_warn: 50
-    pose_no_update_count_threshold_error: 250
+    pose_no_update_count_threshold_error: 100
     twist_no_update_count_threshold_warn: 50
-    twist_no_update_count_threshold_error: 250
+    twist_no_update_count_threshold_error: 100
 
     # for velocity measurement limitation (Set 0.0 if you want to ignore)
     threshold_observable_velocity_mps: 0.0 # [m/s]
diff --git a/system/system_error_monitor/config/diagnostic_aggregator/localization.param.yaml b/system/system_error_monitor/config/diagnostic_aggregator/localization.param.yaml
index 2d0b2b00af343..f203eee79601f 100644
--- a/system/system_error_monitor/config/diagnostic_aggregator/localization.param.yaml
+++ b/system/system_error_monitor/config/diagnostic_aggregator/localization.param.yaml
@@ -29,3 +29,13 @@
               path: localization_accuracy
               contains: [": localization_accuracy"]
               timeout: 1.0
+
+            # This diagnostic should ideally be avoided in terms of Fault Tree Analysis (FTA) compatibility.
+            # However, we may need this since the localization accuracy is still not reliable enough and may produce
+            # false positives. Thus, NOTE that this diagnostic should be removed in the future when the localization accuracy
+            # is reliable enough.
+            sensor_fusion_status:
+              type: diagnostic_aggregator/GenericAnalyzer
+              path: sensor_fusion_status
+              contains: ["localization: ekf_localizer"]
+              timeout: 1.0