Index: firmware/App/Controllers/PresOccl.c
===================================================================
diff -u -r7499a42cc0f906f9a4a947c82c5b4615217ce7e5 -rb1f086e7cd292d5a97a7265075400274d60d4fbf
--- firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision 7499a42cc0f906f9a4a947c82c5b4615217ce7e5)
+++ firmware/App/Controllers/PresOccl.c	(.../PresOccl.c)	(revision b1f086e7cd292d5a97a7265075400274d60d4fbf)
@@ -22,7 +22,8 @@
 #include "NVDataMgmt.h"
 #include "OperationModes.h"
 #include "PersistentAlarm.h"
-#include "SystemCommMessages.h"
+#include "SystemCommMessages.h"
+#include "SelfTests.h"
 #include "TaskGeneral.h"
 #include "Temperatures.h"
 #include "Timers.h"
@@ -69,6 +70,7 @@
 
 #define PSI_TO_MMHG                         ( 51.7149F )                                    ///< Conversion factor for converting PSI to mmHg.
 
+// The new arterial pressure sensor is the same as the venous pressure sensor
 #define VENOUS_PRESSURE_NORMAL_OP           0                                               ///< Venous pressure status bits indicate normal operation.
 #define VENOUS_PRESSURE_CMD_MODE            1                                               ///< Venous pressure status bits indicate sensor in command mode.
 #define VENOUS_PRESSURE_STALE_DATA          2                                               ///< Venous pressure status bits indicate data is stale (no new data since last fpga read).
@@ -709,7 +711,7 @@
 static void checkOcclusions( void )
 {
     U32 bpOccl = getMeasuredBloodPumpOcclusion();
-    BOOL outOfRange = ( bpOccl < MIN_OCCLUSION_COUNTS || bpOccl > MAX_OCCLUSION_COUNTS ? TRUE : FALSE );
+    BOOL outOfRange = ( bpOccl < MIN_OCCLUSION_COUNTS || bpOccl > MAX_OCCLUSION_COUNTS ? TRUE : FALSE );
 
 #ifndef _RELEASE_
     if ( getSoftwareConfigStatus( SW_CONFIG_DISABLE_PRESSURE_CHECKS ) != SW_CONFIG_ENABLE_VALUE )
@@ -721,14 +723,37 @@
             SET_ALARM_WITH_1_U32_DATA( ALARM_ID_HD_BP_OCCLUSION_OUT_OF_RANGE, bpOccl );
         }
 
-        // Check for occlusion
-        if ( bpOccl > ( OCCLUSION_THRESHOLD_OFFSET + bloodPumpOcclusionAfterCartridgeInstall ) )
+        // Check for occlusion in PreTreatment modes when the cartridge is installed
+        // and setOcclusionInstallLevel has been called.
+        if( MODE_PRET == getCurrentOperationMode() )
         {
-            signalBloodPumpHardStop();  // Stop pump immediately
-            SET_ALARM_WITH_1_U32_DATA( ALARM_ID_OCCLUSION_BLOOD_PUMP, bpOccl )
+            if( getPreTreatmentSubState() > HD_PRE_TREATMENT_CART_INSTALL_STATE && getDrySelfTestsState() > DRY_SELF_TESTS_START_STATE )
+            {
+                // Check for occlusion
+                if ( bpOccl > ( OCCLUSION_THRESHOLD_OFFSET + bloodPumpOcclusionAfterCartridgeInstall ) )
+                {
+                    signalBloodPumpHardStop();  // Stop pump immediately
+                    SET_ALARM_WITH_1_U32_DATA( ALARM_ID_OCCLUSION_BLOOD_PUMP, bpOccl )
+                }
+            }
         }
-        else
+        // Check for occlusion in PreTreatment modes where pumps are moving
+        else if( MODE_TREA == getCurrentOperationMode() )
         {
+            if( TREATMENT_STOP_STATE != getTreatmentState())
+            {
+                // Check for occlusion
+                if ( bpOccl > ( OCCLUSION_THRESHOLD_OFFSET + bloodPumpOcclusionAfterCartridgeInstall ) )
+                {
+                    signalBloodPumpHardStop();  // Stop pump immediately
+                    SET_ALARM_WITH_1_U32_DATA( ALARM_ID_OCCLUSION_BLOOD_PUMP, bpOccl )
+                }
+            }
+        }
+
+        // Clear alarm regardless of op mode once conditions are met.
+        if ( bpOccl <= ( OCCLUSION_CLEAR_THRESHOLD_OFFSET + bloodPumpOcclusionAfterCartridgeInstall ) )
+        {
             clearAlarmCondition( ALARM_ID_OCCLUSION_BLOOD_PUMP );
         }
     }