Index: firmware/App/Modes/Rinseback.c
===================================================================
diff -u -re45524455c005d4fa1734efcbaf7ed0499302670 -r764d85698b625d8b8fc1f53d60b6c0f10dad82b8
--- firmware/App/Modes/Rinseback.c	(.../Rinseback.c)	(revision e45524455c005d4fa1734efcbaf7ed0499302670)
+++ firmware/App/Modes/Rinseback.c	(.../Rinseback.c)	(revision 764d85698b625d8b8fc1f53d60b6c0f10dad82b8)
@@ -39,6 +39,7 @@
 
 #define TARGET_RINSEBACK_VOLUME_ML                  300.0                   ///< Target rinseback volume to deliver back to the patient (in mL).  TODO - get from Systems when available
 #define MAX_TOTAL_ADDITIONAL_RINSEBACK_VOLUME_ML    300.0                   ///< Maximum total additional rinseback volume allowed : all additionals (in mL).
+#define MAX_RINSEBACK_VOLUME_ERROR_ML                60.0                   ///< Maximum error in total additional rinseback volume (20% of total).
 #define TARGET_ADDITIONAL_RINSEBACK_VOLUME_ML        10.0                   ///< Target rinseback volume for an additional volume request (in mL).
 #define RINSEBACK_FLOW_RATE_ADJ_ML_MIN               25                     ///< Adjustment amount (in mL/min) to apply when user requests increase/decrease in flow rate.
 #define MIN_RINSEBACK_FLOW_RATE_ML_MIN               50                     ///< Minimum rinseback flow rate (in mL/min).
@@ -63,12 +64,11 @@
 static U32  rinsebackRate_mL_min;                                           ///< Rinseback rate to use/adjust for this current rinseback only.
 static U32  rinsebackTimerCtr;                                              ///< Timer counter for time spent in rinseback sub-mode.
 
-static OVERRIDE_F32_T  cumulativeRinsebackVolume_mL = { 0.0, 0.0, 0.0, 0 };    ///< Total cumulative rinseback volume (in mL).
+static OVERRIDE_F32_T  cumulativeRinsebackVolume_mL = { 0.0, 0.0, 0.0, 0 }; ///< Total cumulative rinseback volume (in mL) from measured blood flow rate.
+static F32  expectedRinsebackVolume_mL = 0.0;                               ///< Total cumulative rinseback volume (in mL) expected based on target blood flow rate.
 static F32  targetRinsebackVolumePlusAdditional_mL;                         ///< Target rinseback volume w/ additional volume(s) added (in mL).
 static F32  additionalRinsebackVolume_mL;                                   ///< Total volume (in mL) delivered so far for additional volume request.
 static F32  totalAdditionalRinsebackVolume_mL;                              ///< Total accumulated volume (in mL) delivered so far for all additional volumes combined.
-static S32  rinsebackMotorCount;                                            ///< The cumulative sum of BP motor encoder counts used for independent rinseback volume check.
-static U32  rinsebackLastMotorCount;                                        ///< The last BP motor encoder count read for independent rinseback volume check.
 static U32  rinsebackAdditionalTimerCtr;                                    ///< Timer counter for duration of an additional rinseback delivery.
 static U32  rinsebackPublishTimerCtr;                                       ///< Timer counter for determining interval for rinseback status to be published.
 /// Interval (in task intervals) at which to publish rinseback data to CAN bus.
@@ -128,10 +128,9 @@
     targetRinsebackVolumePlusAdditional_mL = TARGET_RINSEBACK_VOLUME_ML;
     rinsebackTimerCtr = 0;
     cumulativeRinsebackVolume_mL.data = 0.0;
+    expectedRinsebackVolume_mL = 0.0;
     additionalRinsebackVolume_mL = 0.0;
     totalAdditionalRinsebackVolume_mL = 0.0;
-    rinsebackMotorCount = 0;
-    rinsebackLastMotorCount = getBloodPumpMotorCount();
     rinsebackAdditionalTimerCtr = 0;
     rinsebackPublishTimerCtr = 0;
     resetRinsebackFlags();
@@ -326,7 +325,6 @@
     // Has user requested rinseback start?
     if ( TRUE == startRinsebackRequested )
     {
-        rinsebackLastMotorCount = getBloodPumpMotorCount();
         setupForRinsebackDelivery( rinsebackRate_mL_min );
         // From moment we start rinseback, we consider blood side of dialyzer no longer fully primed
         setBloodIsPrimed( FALSE );
@@ -370,6 +368,7 @@
 
     // Update rinseback volume delivered so far
     cumulativeRinsebackVolume_mL.data += ( getMeasuredBloodFlowRate() * RINSEBACK_FLOW_INTEGRATOR );
+    expectedRinsebackVolume_mL += ( (F32)getTargetBloodFlowRate() * RINSEBACK_FLOW_INTEGRATOR );
 
     // Has user requested to end rinseback?
     if ( TRUE == endRinsebackRequested )
@@ -401,7 +400,7 @@
     }
 #ifndef DISABLE_PUMP_FLOW_CHECKS
     // Is rinseback taking too long?
-    else if ( TBD )
+    else if ( fabs( expectedRinsebackVolume_mL - getRinsebackVolume() ) > MAX_RINSEBACK_VOLUME_ERROR_ML )
     {
         setRinsebackIsCompleted( TRUE );
         setupForRinsebackStopOrPause();