diff --git a/Firmware/ultralcd.cpp b/Firmware/ultralcd.cpp
index bee46ca21..79f56b705 100644
--- a/Firmware/ultralcd.cpp
+++ b/Firmware/ultralcd.cpp
@@ -165,7 +165,7 @@ static bool lcd_selfcheck_pulleys(int axis);
 #endif //TMC2130
 
 static bool lcd_selfcheck_check_heater(bool _isbed);
-enum class testScreen
+enum class testScreen : uint_least8_t
 {
     extruderFan,
     printFan,
@@ -184,6 +184,22 @@ enum class testScreen
     home,
 };
 
+enum class TestError : uint_least8_t
+{
+    unused,
+    heater,
+    bed,
+    endstops,
+    motor,
+    endstop,
+    printFan,
+    extruderFan,
+    pulley,
+    axis,
+    swappedFan,
+    wiringFsensor,
+};
+
 static int  lcd_selftest_screen(testScreen screen, int _progress, int _progress_scale, bool _clear, int _delay);
 static void lcd_selftest_screen_step(int _row, int _col, int _state, const char *_name, const char *_indicator);
 static bool lcd_selftest_manual_fan_check(int _fan, bool check_opposite);
@@ -194,7 +210,7 @@ static bool lcd_selftest_fan_dialog(int _fan);
 static bool lcd_selftest_fsensor();
 #endif //PAT9125
 static bool selftest_irsensor();
-static void lcd_selftest_error(int _error_no, const char *_error_1, const char *_error_2);
+static void lcd_selftest_error(TestError error, const char *_error_1, const char *_error_2);
 static void lcd_colorprint_change();
 #ifdef SNMM
 static int get_ext_nr();
@@ -7184,7 +7200,7 @@ static bool lcd_selfcheck_axis_sg(unsigned char axis) {
 			if (axis == Y_AXIS) _error_1 = "Y";
 			if (axis == Z_AXIS) _error_1 = "Z";
 
-			lcd_selftest_error(9, _error_1, NULL);
+			lcd_selftest_error(TestError::axis, _error_1, NULL);
 			current_position[axis] = 0;
 			plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
 			reset_crash_det(axis);
@@ -7202,7 +7218,7 @@ static bool lcd_selfcheck_axis_sg(unsigned char axis) {
 			if (axis == Y_AXIS) _error_1 = "Y";
 			if (axis == Z_AXIS) _error_1 = "Z";
 
-			lcd_selftest_error(8, _error_1, NULL);
+			lcd_selftest_error(TestError::pulley, _error_1, NULL);
 			current_position[axis] = 0;
 			plan_set_position(current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS]);
 			reset_crash_det(axis);
@@ -7309,11 +7325,11 @@ static bool lcd_selfcheck_axis(int _axis, int _travel)
 
 		if (_travel_done >= _travel)
 		{
-			lcd_selftest_error(5, _error_1, _error_2);
+			lcd_selftest_error(TestError::endstop, _error_1, _error_2);
 		}
 		else
 		{
-			lcd_selftest_error(4, _error_1, _error_2);
+			lcd_selftest_error(TestError::motor, _error_1, _error_2);
 		}
 	}
 
@@ -7479,12 +7495,12 @@ static bool lcd_selfcheck_check_heater(bool _isbed)
 		}
 		else
 		{
-			lcd_selftest_error(1, "", "");
+			lcd_selftest_error(TestError::heater, "", "");
 		}
 	}
 	else
 	{
-		lcd_selftest_error(2, "", "");
+		lcd_selftest_error(TestError::bed, "", "");
 	}
 
 	manage_heater();
@@ -7493,7 +7509,7 @@ static bool lcd_selfcheck_check_heater(bool _isbed)
 	return _stepresult;
 
 }
-static void lcd_selftest_error(int _error_no, const char *_error_1, const char *_error_2)
+static void lcd_selftest_error(TestError testError, const char *_error_1, const char *_error_2)
 {
 	lcd_beeper_quick_feedback();
 
@@ -7509,21 +7525,21 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 	lcd_set_cursor(0, 1);
 	lcd_puts_P(_i("Please check :"));////MSG_SELFTEST_PLEASECHECK c=0 r=0
 
-	switch (_error_no)
+	switch (testError)
 	{
-	case 1:
+	case TestError::heater:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Heater/Thermistor"));////MSG_SELFTEST_HEATERTHERMISTOR c=0 r=0
 		lcd_set_cursor(0, 3);
 		lcd_puts_P(_i("Not connected"));////MSG_SELFTEST_NOTCONNECTED c=0 r=0
 		break;
-	case 2:
+	case TestError::bed:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Bed / Heater"));////MSG_SELFTEST_BEDHEATER c=0 r=0
 		lcd_set_cursor(0, 3);
 		lcd_puts_P(_T(MSG_SELFTEST_WIRINGERROR));
 		break;
-	case 3:
+	case TestError::endstops:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Endstops"));////MSG_SELFTEST_ENDSTOPS c=0 r=0
 		lcd_set_cursor(0, 3);
@@ -7531,7 +7547,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(17, 3);
 		lcd_print(_error_1);
 		break;
-	case 4:
+	case TestError::motor:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_T(MSG_SELFTEST_MOTOR));
 		lcd_set_cursor(18, 2);
@@ -7541,7 +7557,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_2);
 		break;
-	case 5:
+	case TestError::endstop:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Endstop not hit"));////MSG_SELFTEST_ENDSTOP_NOTHIT c=20 r=1
 		lcd_set_cursor(0, 3);
@@ -7549,7 +7565,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 6:
+	case TestError::printFan:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_T(MSG_SELFTEST_COOLING_FAN));
 		lcd_set_cursor(0, 3);
@@ -7557,7 +7573,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 7:
+	case TestError::extruderFan:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_T(MSG_SELFTEST_EXTRUDER_FAN));
 		lcd_set_cursor(0, 3);
@@ -7565,7 +7581,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 8:
+	case TestError::pulley:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Loose pulley"));////MSG_LOOSE_PULLEY c=20 r=1
 		lcd_set_cursor(0, 3);
@@ -7573,7 +7589,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 9:
+	case TestError::axis:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Axis length"));////MSG_SELFTEST_AXIS_LENGTH c=0 r=0
 		lcd_set_cursor(0, 3);
@@ -7581,7 +7597,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 10:
+	case TestError::swappedFan:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Front/left fans"));////MSG_SELFTEST_FANS c=0 r=0
 		lcd_set_cursor(0, 3);
@@ -7589,7 +7605,7 @@ static void lcd_selftest_error(int _error_no, const char *_error_1, const char *
 		lcd_set_cursor(18, 3);
 		lcd_print(_error_1);
 		break;
-	case 11: 
+	case TestError::wiringFsensor:
 		lcd_set_cursor(0, 2);
 		lcd_puts_P(_i("Filament sensor"));////MSG_FILAMENT_SENSOR c=20 r=0
 		lcd_set_cursor(0, 3);
@@ -7796,7 +7812,7 @@ static bool lcd_selftest_manual_fan_check(int _fan, bool check_opposite)
 static bool lcd_selftest_fan_dialog(int _fan)
 {
 	bool _result = true;
-	int _errno = 7;
+	TestError testError = TestError::extruderFan;
 	switch (_fan) {
 	case 0:
 		fanSpeed = 0;
@@ -7851,7 +7867,7 @@ static bool lcd_selftest_fan_dialog(int _fan)
 		printf_P(PSTR("Print fan speed: %d \n"), fan_speed[1]);
 		printf_P(PSTR("Extr fan speed: %d \n"), fan_speed[0]);
 		if (!fan_speed[1]) {
-			_result = false; _errno = 6; //print fan not spinning
+			_result = false; testError = TestError::printFan;
 		}
 #ifdef FAN_SOFT_PWM 
 		else {
@@ -7862,10 +7878,10 @@ static bool lcd_selftest_fan_dialog(int _fan)
 			_result = lcd_selftest_manual_fan_check(1, true); //turn on print fan and check that left extruder fan is not spinning
 			if (_result) {
 				_result = lcd_selftest_manual_fan_check(1, false); //print fan is stil turned on; check that it is spinning
-				if (!_result) _errno = 6; //print fan not spinning
+				if (!_result) testError = TestError::printFan;
 			}
 			else {
-				_errno = 10; //swapped fans
+			    testError = TestError::swappedFan;
 			}
 		}
 
@@ -7877,7 +7893,7 @@ static bool lcd_selftest_fan_dialog(int _fan)
 	}
 	if (!_result)
 	{
-		lcd_selftest_error(_errno, NULL, NULL);
+		lcd_selftest_error(testError, NULL, NULL);
 	}
 	return _result;
 }