diff --git a/Marlin/Conditionals_post.h b/Marlin/Conditionals_post.h
index e96ffb7b9..4dc5b423a 100644
--- a/Marlin/Conditionals_post.h
+++ b/Marlin/Conditionals_post.h
@@ -487,15 +487,19 @@
   #define HAS_Z2_MIN (PIN_EXISTS(Z2_MIN))
   #define HAS_Z2_MAX (PIN_EXISTS(Z2_MAX))
   #define HAS_Z_MIN_PROBE_PIN (PIN_EXISTS(Z_MIN_PROBE))
+  #define HAS_SOLENOID_0 (PIN_EXISTS(SOL0))
   #define HAS_SOLENOID_1 (PIN_EXISTS(SOL1))
   #define HAS_SOLENOID_2 (PIN_EXISTS(SOL2))
   #define HAS_SOLENOID_3 (PIN_EXISTS(SOL3))
+  #define HAS_SOLENOID_4 (PIN_EXISTS(SOL4))
   #define HAS_MICROSTEPS_X (PIN_EXISTS(X_MS1))
   #define HAS_MICROSTEPS_Y (PIN_EXISTS(Y_MS1))
   #define HAS_MICROSTEPS_Z (PIN_EXISTS(Z_MS1))
   #define HAS_MICROSTEPS_E0 (PIN_EXISTS(E0_MS1))
   #define HAS_MICROSTEPS_E1 (PIN_EXISTS(E1_MS1))
   #define HAS_MICROSTEPS_E2 (PIN_EXISTS(E2_MS1))
+  #define HAS_MICROSTEPS_E3 (PIN_EXISTS(E3_MS1))
+  #define HAS_MICROSTEPS_E4 (PIN_EXISTS(E4_MS1))
   #define HAS_MICROSTEPS (HAS_MICROSTEPS_X || HAS_MICROSTEPS_Y || HAS_MICROSTEPS_Z || HAS_MICROSTEPS_E0 || HAS_MICROSTEPS_E1 || HAS_MICROSTEPS_E2)
   #define HAS_STEPPER_RESET (PIN_EXISTS(STEPPER_RESET))
   #define HAS_X_ENABLE (PIN_EXISTS(X_ENABLE))
diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 6b9152cd8..2ca660c99 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -7599,21 +7599,26 @@ inline void gcode_M303() {
       case 0:
         OUT_WRITE(SOL0_PIN, HIGH);
         break;
-        #if HAS_SOLENOID_1
+        #if HAS_SOLENOID_1 && EXTRUDERS > 1
           case 1:
             OUT_WRITE(SOL1_PIN, HIGH);
             break;
         #endif
-        #if HAS_SOLENOID_2
+        #if HAS_SOLENOID_2 && EXTRUDERS > 2
           case 2:
             OUT_WRITE(SOL2_PIN, HIGH);
             break;
         #endif
-        #if HAS_SOLENOID_3
+        #if HAS_SOLENOID_3 && EXTRUDERS > 3
           case 3:
             OUT_WRITE(SOL3_PIN, HIGH);
             break;
         #endif
+        #if HAS_SOLENOID_4 && EXTRUDERS > 4
+          case 4:
+            OUT_WRITE(SOL4_PIN, HIGH);
+            break;
+        #endif
       default:
         SERIAL_ECHO_START;
         SERIAL_ECHOLNPGM(MSG_INVALID_SOLENOID);
@@ -7625,9 +7630,18 @@ inline void gcode_M303() {
 
   void disable_all_solenoids() {
     OUT_WRITE(SOL0_PIN, LOW);
-    OUT_WRITE(SOL1_PIN, LOW);
-    OUT_WRITE(SOL2_PIN, LOW);
-    OUT_WRITE(SOL3_PIN, LOW);
+    #if HAS_SOLENOID_1 && EXTRUDERS > 1
+      OUT_WRITE(SOL1_PIN, LOW);
+    #endif
+    #if HAS_SOLENOID_2 && EXTRUDERS > 2
+      OUT_WRITE(SOL2_PIN, LOW);
+    #endif
+    #if HAS_SOLENOID_3 && EXTRUDERS > 3
+      OUT_WRITE(SOL3_PIN, LOW);
+    #endif
+    #if HAS_SOLENOID_4 && EXTRUDERS > 4
+      OUT_WRITE(SOL4_PIN, LOW);
+    #endif
   }
 
   /**
diff --git a/Marlin/stepper.cpp b/Marlin/stepper.cpp
index 339e6bf9b..16594b5f6 100644
--- a/Marlin/stepper.cpp
+++ b/Marlin/stepper.cpp
@@ -1076,6 +1076,9 @@ void Stepper::init() {
   #if HAS_E3_STEP
     E_AXIS_INIT(3);
   #endif
+  #if HAS_E4_STEP
+    E_AXIS_INIT(4);
+  #endif
 
   // waveform generation = 0100 = CTC
   CBI(TCCR1B, WGM13);
@@ -1477,6 +1480,18 @@ void Stepper::report_positions() {
       SET_OUTPUT(E1_MS1_PIN);
       SET_OUTPUT(E1_MS2_PIN);
     #endif
+    #if HAS_MICROSTEPS_E2
+      SET_OUTPUT(E2_MS1_PIN);
+      SET_OUTPUT(E2_MS2_PIN);
+    #endif
+    #if HAS_MICROSTEPS_E3
+      SET_OUTPUT(E3_MS1_PIN);
+      SET_OUTPUT(E3_MS2_PIN);
+    #endif
+    #if HAS_MICROSTEPS_E4
+      SET_OUTPUT(E4_MS1_PIN);
+      SET_OUTPUT(E4_MS2_PIN);
+    #endif
     static const uint8_t microstep_modes[] = MICROSTEP_MODES;
     for (uint16_t i = 0; i < COUNT(microstep_modes); i++)
       microstep_mode(i, microstep_modes[i]);
@@ -1497,6 +1512,15 @@ void Stepper::report_positions() {
       #if HAS_MICROSTEPS_E1
         case 4: WRITE(E1_MS1_PIN, ms1); break;
       #endif
+      #if HAS_MICROSTEPS_E2
+        case 5: WRITE(E2_MS1_PIN, ms1); break;
+      #endif
+      #if HAS_MICROSTEPS_E3
+        case 6: WRITE(E3_MS1_PIN, ms1); break;
+      #endif
+      #if HAS_MICROSTEPS_E4
+        case 7: WRITE(E4_MS1_PIN, ms1); break;
+      #endif
     }
     if (ms2 >= 0) switch (driver) {
       case 0: WRITE(X_MS2_PIN, ms2); break;
@@ -1512,6 +1536,15 @@ void Stepper::report_positions() {
       #if HAS_MICROSTEPS_E1
         case 4: WRITE(E1_MS2_PIN, ms2); break;
       #endif
+      #if HAS_MICROSTEPS_E2
+        case 5: WRITE(E2_MS2_PIN, ms2); break;
+      #endif
+      #if HAS_MICROSTEPS_E3
+        case 6: WRITE(E3_MS2_PIN, ms2); break;
+      #endif
+      #if HAS_MICROSTEPS_E4
+        case 7: WRITE(E4_MS2_PIN, ms2); break;
+      #endif
     }
   }
 
@@ -1550,6 +1583,21 @@ void Stepper::report_positions() {
       SERIAL_PROTOCOL(READ(E1_MS1_PIN));
       SERIAL_PROTOCOLLN(READ(E1_MS2_PIN));
     #endif
+    #if HAS_MICROSTEPS_E2
+      SERIAL_PROTOCOLPGM("E2: ");
+      SERIAL_PROTOCOL(READ(E2_MS1_PIN));
+      SERIAL_PROTOCOLLN(READ(E2_MS2_PIN));
+    #endif
+    #if HAS_MICROSTEPS_E3
+      SERIAL_PROTOCOLPGM("E3: ");
+      SERIAL_PROTOCOL(READ(E3_MS1_PIN));
+      SERIAL_PROTOCOLLN(READ(E3_MS2_PIN));
+    #endif
+    #if HAS_MICROSTEPS_E4
+      SERIAL_PROTOCOLPGM("E4: ");
+      SERIAL_PROTOCOL(READ(E4_MS1_PIN));
+      SERIAL_PROTOCOLLN(READ(E4_MS2_PIN));
+    #endif
   }
 
 #endif // HAS_MICROSTEPS
diff --git a/Marlin/thermistortables.h b/Marlin/thermistortables.h
index 05ec9a30a..3777cf2e4 100644
--- a/Marlin/thermistortables.h
+++ b/Marlin/thermistortables.h
@@ -226,6 +226,15 @@
     #define HEATER_3_RAW_LO_TEMP 0
   #endif
 #endif
+#ifndef HEATER_4_RAW_HI_TEMP
+  #ifdef HEATER_4_USES_THERMISTOR
+    #define HEATER_4_RAW_HI_TEMP 0
+    #define HEATER_4_RAW_LO_TEMP 16383
+  #else
+    #define HEATER_4_RAW_HI_TEMP 16383
+    #define HEATER_4_RAW_LO_TEMP 0
+  #endif
+#endif
 #ifndef HEATER_BED_RAW_HI_TEMP
   #ifdef BED_USES_THERMISTOR
     #define HEATER_BED_RAW_HI_TEMP 0