diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 420bd00abb..ebc36bc1af 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -1177,19 +1177,21 @@ void process_commands()
         //ClearToSend();
         return;
       }
-      //break;
+      break;
     case 2: // G2  - CW ARC
       if(Stopped == false) {
         get_arc_coordinates();
         prepare_arc_move(true);
         return;
       }
+      break;
     case 3: // G3  - CCW ARC
       if(Stopped == false) {
         get_arc_coordinates();
         prepare_arc_move(false);
         return;
       }
+      break;
     case 4: // G4 dwell
       LCD_MESSAGEPGM(MSG_DWELL);
       codenum = 0;
@@ -1797,7 +1799,7 @@ void process_commands()
         int pin_number = LED_PIN;
         if (code_seen('P') && pin_status >= 0 && pin_status <= 255)
           pin_number = code_value();
-        for(int8_t i = 0; i < (int8_t)sizeof(sensitive_pins); i++)
+        for(int8_t i = 0; i < (int8_t)(sizeof(sensitive_pins)/sizeof(int)); i++)
         {
           if (sensitive_pins[i] == pin_number)
           {
@@ -2151,8 +2153,9 @@ void process_commands()
       }
       break;
     case 85: // M85
-      code_seen('S');
-      max_inactive_time = code_value() * 1000;
+      if(code_seen('S')) {
+        max_inactive_time = code_value() * 1000;
+      }
       break;
     case 92: // M92
       for(int8_t i=0; i < NUM_AXIS; i++)
@@ -2273,6 +2276,7 @@ void process_commands()
           if(tmp_extruder >= EXTRUDERS) {
             SERIAL_ECHO_START;
             SERIAL_ECHO(MSG_M200_INVALID_EXTRUDER);
+            break;
           }
         }
         volumetric_multiplier[tmp_extruder] = 1 / area;
diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 737d075754..a199f4e742 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -179,7 +179,7 @@ void PID_autotune(float temp, int extruder, int ncycles)
   float Kp, Ki, Kd;
   float max = 0, min = 10000;
 
-  if ((extruder > EXTRUDERS)
+  if ((extruder >= EXTRUDERS)
   #if (TEMP_BED_PIN <= -1)
        ||(extruder < 0)
   #endif
@@ -909,7 +909,7 @@ void disable_heater()
    #endif
   #endif
      
-  #if defined(TEMP_1_PIN) && TEMP_1_PIN > -1
+  #if defined(TEMP_1_PIN) && TEMP_1_PIN > -1 && EXTRUDERS > 1
     target_temperature[1]=0;
     soft_pwm[1]=0;
     #if defined(HEATER_1_PIN) && HEATER_1_PIN > -1 
@@ -917,7 +917,7 @@ void disable_heater()
     #endif
   #endif
       
-  #if defined(TEMP_2_PIN) && TEMP_2_PIN > -1
+  #if defined(TEMP_2_PIN) && TEMP_2_PIN > -1 && EXTRUDERS > 2
     target_temperature[2]=0;
     soft_pwm[2]=0;
     #if defined(HEATER_2_PIN) && HEATER_2_PIN > -1