Index: firmware/App/Modes/FPModes/ModePreGenPermeate.c
===================================================================
diff -u -r8d27c30384b9bce99420fc0751d359c4b3871ea4 -r3e1af7cc2576e347ab8bdf2f400196b2301def07
--- firmware/App/Modes/FPModes/ModePreGenPermeate.c	(.../ModePreGenPermeate.c)	(revision 8d27c30384b9bce99420fc0751d359c4b3871ea4)
+++ firmware/App/Modes/FPModes/ModePreGenPermeate.c	(.../ModePreGenPermeate.c)	(revision 3e1af7cc2576e347ab8bdf2f400196b2301def07)
@@ -7,8 +7,8 @@
 *
 * @file    ModePreGenPermeate.c
 *
-* @author  (last)      “rkallala”
-* @date    (last)      29-Jan-2026
+* @author  (last)      Raghu Kallala
+* @date    (last)      31-Mar-2026
 *
 * @author  (original)  Michael Garthwaite
 * @date    (original)  08-Sep-2025
@@ -18,6 +18,7 @@
 #include "BoostPump.h"
 #include "FPModeStandby.h"
 #include "FPOperationModes.h"
+#include "Level.h"
 #include "MessageSupport.h"
 #include "Messaging.h"
 #include "ModeGenPermeate.h"
@@ -550,4 +551,89 @@
     return result;
 }
 
+/*********************************************************************//**
+ * @brief
+ * The testValidatePreGenPChangeReq function validate whether requested
+ * sub mode change is legal or not.
+ * @details \b Inputs: none
+ * @details \b Outputs: none
+ * @param newSubMode the enumerated sub state of the mode.
+ * @return TRUE if request is legal, FALSE if not.
+ *************************************************************************/
+BOOL testValidatePreGenPChangeReq( U32 newSubMode )
+{
+    BOOL result = FALSE;
+    LEVEL_STATE_T level = getLevelStatus( P25_LEVL );
+
+    if ( newSubMode < NUM_OF_FP_PRE_GENW_MODE_STATES )
+    {
+        switch ( newSubMode )
+        {
+            case FP_PRE_GENP_CONCENTRATE_FLUSH:
+                result = (( LEVEL_STATE_HIGH == level ) ? TRUE : FALSE);
+                break;
+
+            case FP_PRE_GENP_INLET_PRESSURE_CHECK:
+            case FP_PRE_GENP_FILTER_FLUSH:
+            case FP_PRE_GENP_PERMEATE_FLUSH:
+            case FP_PRE_GENP_VERIFY_WATER:
+                result = TRUE;
+                break;
+
+            // TODO change once pause state is implemented
+            case FP_PRE_GENP_PAUSED:
+            default:
+                break;
+        }
+    }
+
+    return result;
+}
+
+/*********************************************************************//**
+ * @brief
+ * The testSignalNewPreGenPSubMode function requests transition to a new
+ * PreGen Permeate sub mode.
+ * @details \b Inputs: none
+ * @details \b Outputs: preGenPState
+ * @param newSubMode the enumerated sub state of the mode.
+ * @return none
+ *************************************************************************/
+void testSignalNewPreGenPSubMode( U32 newSubMode )
+{
+    if ( newSubMode < NUM_OF_FP_PRE_GENW_MODE_STATES )
+    {
+        preGenPState = (FP_PRE_GENP_MODE_STATE_T)newSubMode;
+        // handle the prerequisite if any
+        switch ( newSubMode )
+        {
+            case FP_PRE_GENP_INLET_PRESSURE_CHECK:
+                resetInletPressureCheckSignals();
+                break;
+
+            case FP_PRE_GENP_FILTER_FLUSH:
+                resetFilterFlushSignals();
+                signalStartFilterFlush();
+                break;
+
+            case FP_PRE_GENP_PERMEATE_FLUSH:
+                resetPermeateFlushSignals();
+                signalStartPermeateFlush();
+                break;
+
+            case FP_PRE_GENP_CONCENTRATE_FLUSH:
+                resetConcentrateFlushSignals();
+                signalStartConcentrateFlush();
+                break;
+
+            // Require no special handling for now (update if required in future)
+            case FP_PRE_GENP_VERIFY_WATER:
+            case FP_PRE_GENP_PAUSED:
+            default:
+                break;
+        }
+        setModePreGenPTransition( preGenPState );
+    }
+}
+
 /**@}*/