diff --git a/fw/Core/Src/main.c b/fw/Core/Src/main.c
index cb0ab20..c4f630e 100644
--- a/fw/Core/Src/main.c
+++ b/fw/Core/Src/main.c
@@ -90,9 +90,11 @@ enum
 	REGISTER_NUM_PMC_NUMBER_4_0 = 30016, /* 1 / m^3 */
 	REGISTER_NUM_PMC_NUMBER_10_0 = 30017, /* 1 / m^3 */
 	REGISTER_NUM_TYPICAL_PARTICLE_SIZE = 30018, /* nm */
-	REGISTER_NUM_T_SCD4x = 30019, /* deg C */
-	REGISTER_NUM_T_SCD4x_F = 30020, /* deg F */
-	REGISTER_NUM_RH_SCD4x = 30021 /* % */
+	REGISTER_NUM_READ_ERR_T = 30019, /* deg C */
+	REGISTER_NUM_READ_ERR_RH = 30020, /* deg C */
+	REGISTER_NUM_READ_ERR_CO2 = 30021, /* deg C */
+	REGISTER_NUM_READ_ERR_VOC = 30022, /* deg C */
+	REGISTER_NUM_READ_ERR_PMC = 30023, /* deg C */
 	/* VOC Index has initial blackout beriod, when the data is not ready. VOC index is 0 during this period */
 } data_registers_numbers;
 
@@ -148,6 +150,12 @@ uint8_t sps30_is_connected = 0;
 uint8_t sgp40_is_connected = 0;
 /* Sensirion library for VOC */
 GasIndexAlgorithmParams voc_params;
+/* Sensor return value variables */
+int8_t read_error_temperature;
+int8_t read_error_rh;
+int8_t read_error_co2;
+int8_t read_error_voc;
+int8_t read_error_pmc;
 /* USER CODE END PV */
 
 /* Private function prototypes -----------------------------------------------*/
@@ -461,12 +469,12 @@ int main(void)
 	  {
 		  /* TODO: Check the data */
 		  /* Read SHT4x data (always connected) */
-		  sht4x_measure(&T_SHT4x, &RH_SHT4x);
+		  read_error_temperature = read_error_rh = sht4x_measure(&T_SHT4x, &RH_SHT4x);
 		  TF_SHT4x = CELSIUS_TO_FAHRENHEIT(T_SHT4x);
 		  /* Read SCD4x data (if connected) */
 		  if (scd4x_is_connected == 1)
 		  {
-			  if (scd4x_read_measurement(&CO2, &T_SCD4x, &RH_SCD4x) != SCD4X_OK) {
+			  if ((read_error_co2 = scd4x_read_measurement(&CO2, &T_SCD4x, &RH_SCD4x)) != SCD4X_OK) {
 				  /* read failed, either I2C fail or CRC error */
 				  // TODO something
 			  }
@@ -481,7 +489,7 @@ int main(void)
 		  /* Read SPS30 data (if connected) */
 		  if (sps30_is_connected == 1)
 		  {
-			  sps30_read_measured_values(&PM_SPS30);
+			  read_error_pmc = sps30_read_measured_values(&PM_SPS30);
 		  }
 		  /* TODO: Process data and light a desired color of LED */
 		  /* TODO: Add hystheresis */
@@ -490,7 +498,7 @@ int main(void)
 		  if (sgp40_is_connected == 1)
 		  {
 			  //sgp40_measure_raw_signal(&voc_ticks);
-			  sgp40_measure_raw_signal_compensated(&voc_ticks_compensated, RH_SHT4x, T_SHT4x);
+			  read_error_voc = sgp40_measure_raw_signal_compensated(&voc_ticks_compensated, RH_SHT4x, T_SHT4x);
 //			  sgp40_measure_raw_signal(&voc_ticks);
 			  /* Sensirion VOC library */
 			  GasIndexAlgorithm_process(&voc_params, voc_ticks_compensated, (int32_t*)&voc_index);
@@ -1040,21 +1048,27 @@ int8_t modbus_slave_callback(modbus_transaction_t *transaction)
 						MODBUS_ASSERT(sps30_is_connected);
 						transaction->input_registers[i] = (uint16_t)PM_SPS30.typical_particle_size;
 						break;
-					case REGISTER_NUM_T_SCD4x:
-						transaction->input_registers_signed[i] = (int16_t)T_SCD4x;
-						break;
-					case REGISTER_NUM_T_SCD4x_F:
-						transaction->input_registers_signed[i] = (int16_t)TF_SCD4x;
-						break;
-					case REGISTER_NUM_RH_SCD4x:
-						transaction->input_registers[i] = (uint16_t)RH_SCD4x;
-						break;
 					case REGISTER_NUM_SERIAL_NUMBER_1:
 						transaction->input_registers[i] = (uint16_t)sensor_config.serial_number_1;
 						break;
 					case REGISTER_NUM_SERIAL_NUMBER_2:
 						transaction->input_registers[i] = (uint16_t)sensor_config.serial_number_2;
 						break;
+					case REGISTER_NUM_READ_ERR_T:
+						transaction->input_registers[i] = (uint16_t)read_error_temperature;
+						break;
+					case REGISTER_NUM_READ_ERR_RH:
+						transaction->input_registers[i] = (uint16_t)read_error_rh;
+						break;
+					case REGISTER_NUM_READ_ERR_CO2:
+						transaction->input_registers[i] = (uint16_t)read_error_co2;
+						break;
+					case REGISTER_NUM_READ_ERR_VOC:
+						transaction->input_registers[i] = (uint16_t)read_error_voc;
+						break;
+					case REGISTER_NUM_READ_ERR_PMC:
+						transaction->input_registers[i] = (uint16_t)read_error_pmc;
+						break;
 					default:
 						return MODBUS_ERROR_FUNCTION_NOT_IMPLEMENTED;
 				}