Index: firmware/App/Modes/ModeTreatment.c
===================================================================
diff -u -r96604b790636c66ef21980a4f13ee9f987f12fee -r222b05e39082f727dcfa2d144fa6e040501882f0
--- firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision 96604b790636c66ef21980a4f13ee9f987f12fee)
+++ firmware/App/Modes/ModeTreatment.c	(.../ModeTreatment.c)	(revision 222b05e39082f727dcfa2d144fa6e040501882f0)
@@ -253,7 +253,7 @@
 
     // Direct DD to generate dialysate and bypass while priming blood.
     cmdStartGenerateDialysate( (F32)getTreatmentParameterU32( TREATMENT_PARAM_DIALYSATE_FLOW ), presUFRateMlMin,
-                               getTreatmentParameterF32( TREATMENT_PARAM_DIALYSATE_TEMPERATURE ), TRUE,
+                               getTreatmentParameterF32( TREATMENT_PARAM_DIALYSATE_TEMPERATURE ), DD_GEND_DIALYSATE_BYPASS_STATE,
                                getTreatmentParameterF32( TREATMENT_PARAM_ACID_CONCENTRATE_CONV_FACTOR ),
                                bicarbConvFactor,
                                getTreatmentParameterU32( TREATMENT_PARAM_SODIUM ),
@@ -384,6 +384,8 @@
 
         if ( TREATMENT_ISO_UF_STATE == currentTreatmentState )
         {
+            cmdSetGenDialysateState( DD_GEND_ISOLATED_UF_STATE );
+
             if ( ISOLATED_UF_PAUSED_STATE == getCurrentIsolatedUFState() )
             {
                 cmdChangeQuf( 0.0F );
@@ -874,61 +876,43 @@
 /*********************************************************************//**
  * @brief
  * The handleTreatmentIsoUFState function handles isolated ultrafiltration.
- * @details \b Inputs: treatmentTimeMS, lastTreatmentTimeStamp
- * @details \b Outputs: treatmentTimeMS, isolated UF sub-mode executed
+ * @details \b Inputs: lastTreatmentTimeStamp
+ * @details \b Outputs: isolated UF sub-mode executed
  * @return next treatment mode state
  *************************************************************************/
 static TREATMENT_STATE_T handleTreatmentIsoUFState( void )
 {
     TREATMENT_STATE_T result = TREATMENT_ISO_UF_STATE;
     U32 newTime = getMSTimerCount();
-    U32 msSinceLast = calcTimeBetween( lastTreatmentTimeStamp, newTime );
 
-    // Update treatment time
-    treatmentTimeMS += msSinceLast;
+    // Keep the main HD/HDF treatment timer paused while isolated UF tracks its own session time.
     lastTreatmentTimeStamp = newTime;
 
-    // Prescribed HD/HDF time elapsed during mid-treatment iso UF: end iso UF and wait in END for post-treatment iso UF or POST.
-    if ( ( TRUE == isIsolatedUFMidTreatment() ) &&
-         ( CALC_ELAPSED_TREAT_TIME_IN_SECS() >= presTreatmentTimeSecs ) )
+    execIsolatedUF();
+
+    if ( TRUE == isIsolatedUFCompleted() )
     {
-        treatmentCompleted = TRUE;
         recordCompletedIsolatedUFSession();
-        endIsolatedUFOnUserStop();
-        isolatedUFMidTreatment = FALSE;
-        cmdBypassDialyzer( TRUE );
-        cmdChangeQuf( 0.0F );
-        cmdChangeQd( 0.0F );
-        result = TREATMENT_END_STATE;
-    }
-    else
-    {
-        execIsolatedUF();
 
-        if ( TRUE == isIsolatedUFCompleted() )
+        if ( TRUE == isIsolatedUFMidTreatment() )
         {
-            recordCompletedIsolatedUFSession();
-
-            if ( TRUE == isIsolatedUFMidTreatment() )
-            {
-                resumeDialysisAfterIsolatedUF();
-                result = TREATMENT_DIALYSIS_STATE;
-            }
-            else
-            {
-                treatmentCompleted = TRUE;
-                cmdBypassDialyzer( TRUE );
-                cmdChangeQuf( 0.0F );
-                requestNewOperationMode( MODE_POST );
-                result = TREATMENT_END_STATE;
-            }
+            resumeDialysisAfterIsolatedUF();
+            result = TREATMENT_DIALYSIS_STATE;
         }
-        // Handle alarm page
-        else if ( TRUE == doesAlarmStatusIndicateStop() )
+        else
         {
-            result = enterTreatmentPausedState();
+            treatmentCompleted = TRUE;
+            cmdBypassDialyzer( TRUE );
+            cmdChangeQuf( 0.0F );
+            requestNewOperationMode( MODE_POST );
+            result = TREATMENT_END_STATE;
         }
     }
+    // Handle alarm page
+    else if ( TRUE == doesAlarmStatusIndicateStop() )
+    {
+        result = enterTreatmentPausedState();
+    }
 
     return result;
 }