diff --git a/Core/Inc/imd_monitoring.h b/Core/Inc/imd_monitoring.h
new file mode 100644
index 0000000..553c744
--- /dev/null
+++ b/Core/Inc/imd_monitoring.h
@@ -0,0 +1,36 @@
+#ifndef INC_IMD_MONITORING_H
+#define INC_IMD_MONITORING_H
+
+#include <stdint.h>
+
+#include "stm32f3xx_hal.h"
+
+typedef enum {
+  IMD_STATE_UNKNOWN,
+  IMD_STATE_SHORTCIRCUIT_SUPPLY,
+  IMD_STATE_SHORTCIRCUIT_GND,
+  IMD_STATE_NORMAL,
+  IMD_STATE_UNDERVOLTAGE,
+  IMD_STATE_SST,
+  IMD_STATE_DEV_ERROR,
+  IMD_STATE_GND_FAULT,
+} IMDState;
+
+typedef struct {
+  int ok;
+
+  IMDState state;
+  uint32_t r_iso;
+
+  uint32_t freq;
+  uint32_t duty_cycle;
+  uint32_t last_high;
+} IMDData;
+
+extern IMDData imd_data;
+
+void imd_init(TIM_HandleTypeDef *htim);
+
+void imd_update(void);
+
+#endif // INC_IMD_MONITORING_H
diff --git a/Core/Inc/main.h b/Core/Inc/main.h
index 7cf7526..8c1333c 100644
--- a/Core/Inc/main.h
+++ b/Core/Inc/main.h
@@ -61,6 +61,8 @@ void Error_Handler(void);
 #define HV_MISMATCH_ERR_GPIO_Port GPIOA
 #define RELAY_MISMATCH_ERR_Pin GPIO_PIN_1
 #define RELAY_MISMATCH_ERR_GPIO_Port GPIOA
+#define IMD_M_Pin GPIO_PIN_2
+#define IMD_M_GPIO_Port GPIOA
 #define IMD_OK_Pin GPIO_PIN_3
 #define IMD_OK_GPIO_Port GPIOA
 #define RELAY_CONNECTION_ERR_Pin GPIO_PIN_4
diff --git a/Core/Inc/stm32f3xx_it.h b/Core/Inc/stm32f3xx_it.h
index ba25618..658788a 100644
--- a/Core/Inc/stm32f3xx_it.h
+++ b/Core/Inc/stm32f3xx_it.h
@@ -56,6 +56,7 @@ void DebugMon_Handler(void);
 void PendSV_Handler(void);
 void SysTick_Handler(void);
 void USB_LP_CAN_RX0_IRQHandler(void);
+void TIM1_BRK_TIM15_IRQHandler(void);
 /* USER CODE BEGIN EFP */
 
 /* USER CODE END EFP */
diff --git a/Core/Src/can.c b/Core/Src/can.c
index 2ae20c7..30c62ab 100644
--- a/Core/Src/can.c
+++ b/Core/Src/can.c
@@ -1,5 +1,6 @@
 #include "can.h"
 
+#include "imd_monitoring.h"
 #include "main.h"
 #include "shunt_monitoring.h"
 #include "slave_monitoring.h"
@@ -21,11 +22,17 @@ void can_init(CAN_HandleTypeDef *handle) {
 }
 
 HAL_StatusTypeDef can_send_status() {
-  uint8_t data[6];
+  uint8_t data[8];
   data[0] = ts_state.current_state | (sdc_closed << 7);
   data[1] = roundf(current_soc);
   ftcan_marshal_unsigned(&data[2], min_voltage, 2);
   ftcan_marshal_signed(&data[4], max_temp, 2);
+  data[6] = imd_data.state | (imd_data.ok << 7);
+  if (imd_data.r_iso < 0xFFF) {
+    data[7] = imd_data.r_iso >> 4;
+  } else {
+    data[7] = 0xFF;
+  }
   return ftcan_transmit(CAN_ID_AMS_STATUS, data, sizeof(data));
 }
 
diff --git a/Core/Src/imd_monitoring.c b/Core/Src/imd_monitoring.c
new file mode 100644
index 0000000..4588ecd
--- /dev/null
+++ b/Core/Src/imd_monitoring.c
@@ -0,0 +1,86 @@
+#include "imd_monitoring.h"
+
+#include "main.h"
+
+#define FREQ_TIMER 1000 // Hz
+
+#define FREQ_TOLERANCE 1     // Hz
+#define FREQ_NORMAL 10       // Hz
+#define FREQ_UNDERVOLTAGE 20 // Hz
+#define FREQ_SST 30          // Hz
+#define FREQ_DEV_ERROR 40    // Hz
+#define FREQ_GND_FAULT 50    // Hz
+
+#define RISO_MIN_DUTY_CYCLE 8 // %
+#define RISO_MAX 50000        // kOhm
+
+#define PWM_TIMEOUT 200 // ms
+
+IMDData imd_data;
+
+static TIM_HandleTypeDef *htim;
+
+void imd_init(TIM_HandleTypeDef *handle) {
+  htim = handle;
+  HAL_TIM_IC_Start_IT(htim, TIM_CHANNEL_1);
+  HAL_TIM_IC_Start(htim, TIM_CHANNEL_2);
+
+  imd_data.state = IMD_STATE_UNKNOWN;
+}
+
+void HAL_TIM_IC_CaptureCallback(TIM_HandleTypeDef *handle) {
+  if (handle != htim || htim->Channel != HAL_TIM_ACTIVE_CHANNEL_1) {
+    return;
+  }
+  uint32_t period = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_1);
+  if (period == 0) {
+    // First edge, ignore
+    return;
+  }
+  imd_data.last_high = HAL_GetTick();
+
+  imd_data.freq = FREQ_TIMER / period;
+  uint32_t high_time = HAL_TIM_ReadCapturedValue(htim, TIM_CHANNEL_2);
+  imd_data.duty_cycle = (100 * high_time) / period;
+
+  // Check PWM frequency for state determination
+  if (imd_data.freq > FREQ_NORMAL - FREQ_TOLERANCE &&
+      imd_data.freq < FREQ_NORMAL + FREQ_TOLERANCE) {
+    imd_data.state = IMD_STATE_NORMAL;
+  } else if (imd_data.freq > FREQ_UNDERVOLTAGE - FREQ_TOLERANCE &&
+             imd_data.freq < FREQ_UNDERVOLTAGE + FREQ_TOLERANCE) {
+    imd_data.state = IMD_STATE_UNDERVOLTAGE;
+  } else if (imd_data.freq > FREQ_SST - FREQ_TOLERANCE &&
+             imd_data.freq < FREQ_SST + FREQ_TOLERANCE) {
+    imd_data.state = IMD_STATE_SST;
+  } else if (imd_data.freq > FREQ_DEV_ERROR - FREQ_TOLERANCE &&
+             imd_data.freq < FREQ_DEV_ERROR + FREQ_TOLERANCE) {
+    imd_data.state = IMD_STATE_DEV_ERROR;
+  } else if (imd_data.freq > FREQ_GND_FAULT - FREQ_TOLERANCE &&
+             imd_data.freq < FREQ_GND_FAULT + FREQ_TOLERANCE) {
+    imd_data.state = IMD_STATE_GND_FAULT;
+  } else {
+    imd_data.state = IMD_STATE_UNKNOWN;
+  }
+
+  // Calculate R_iso
+  if (imd_data.state == IMD_STATE_NORMAL ||
+      imd_data.state == IMD_STATE_UNDERVOLTAGE) {
+    if (imd_data.duty_cycle < RISO_MIN_DUTY_CYCLE) {
+      imd_data.r_iso = RISO_MAX;
+    } else {
+      imd_data.r_iso = (90 * 1200) / (imd_data.duty_cycle - 5) - 1200;
+    }
+  }
+}
+
+void imd_update() {
+  imd_data.ok = HAL_GPIO_ReadPin(IMD_OK_GPIO_Port, IMD_OK_Pin);
+  if (HAL_GetTick() - imd_data.last_high > PWM_TIMEOUT) {
+    if (HAL_GPIO_ReadPin(IMD_M_GPIO_Port, IMD_M_Pin) == GPIO_PIN_SET) {
+      imd_data.state = IMD_STATE_SHORTCIRCUIT_SUPPLY;
+    } else {
+      imd_data.state = IMD_STATE_SHORTCIRCUIT_GND;
+    }
+  }
+}
diff --git a/Core/Src/main.c b/Core/Src/main.c
index 260cbc5..8372409 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -22,14 +22,15 @@
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
 #include "can.h"
-#include "soc_estimation.h"
-#include "stm32f3xx_hal.h"
-#include "stm32f3xx_hal_gpio.h"
-
+#include "imd_monitoring.h"
 #include "shunt_monitoring.h"
 #include "slave_monitoring.h"
+#include "soc_estimation.h"
 #include "ts_state_machine.h"
 
+#include "stm32f3xx_hal.h"
+#include "stm32f3xx_hal_gpio.h"
+
 /* USER CODE END Includes */
 
 /* Private typedef -----------------------------------------------------------*/
@@ -130,6 +131,7 @@ int main(void) {
   shunt_init();
   ts_sm_init();
   soc_init();
+  imd_init(&htim15);
   HAL_GPIO_WritePin(AMS_NERROR_GPIO_Port, AMS_NERROR_Pin, GPIO_PIN_SET);
   /* USER CODE END 2 */
 
@@ -147,6 +149,7 @@ int main(void) {
     shunt_check();
     ts_sm_update();
     soc_update();
+    imd_update();
     can_send_status();
 
     loop_delay();
@@ -349,7 +352,7 @@ static void MX_TIM15_Init(void) {
 
   /* USER CODE END TIM15_Init 1 */
   htim15.Instance = TIM15;
-  htim15.Init.Prescaler = 0;
+  htim15.Init.Prescaler = 16000 - 1;
   htim15.Init.CounterMode = TIM_COUNTERMODE_UP;
   htim15.Init.Period = 65535;
   htim15.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
diff --git a/Core/Src/stm32f3xx_hal_msp.c b/Core/Src/stm32f3xx_hal_msp.c
index a1f776a..ca4a8d3 100644
--- a/Core/Src/stm32f3xx_hal_msp.c
+++ b/Core/Src/stm32f3xx_hal_msp.c
@@ -303,13 +303,16 @@ void HAL_TIM_IC_MspInit(TIM_HandleTypeDef* htim_ic)
     /**TIM15 GPIO Configuration
     PA2     ------> TIM15_CH1
     */
-    GPIO_InitStruct.Pin = GPIO_PIN_2;
+    GPIO_InitStruct.Pin = IMD_M_Pin;
     GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
     GPIO_InitStruct.Pull = GPIO_NOPULL;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
     GPIO_InitStruct.Alternate = GPIO_AF9_TIM15;
-    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
+    HAL_GPIO_Init(IMD_M_GPIO_Port, &GPIO_InitStruct);
 
+    /* TIM15 interrupt Init */
+    HAL_NVIC_SetPriority(TIM1_BRK_TIM15_IRQn, 0, 0);
+    HAL_NVIC_EnableIRQ(TIM1_BRK_TIM15_IRQn);
   /* USER CODE BEGIN TIM15_MspInit 1 */
 
   /* USER CODE END TIM15_MspInit 1 */
@@ -336,8 +339,10 @@ void HAL_TIM_IC_MspDeInit(TIM_HandleTypeDef* htim_ic)
     /**TIM15 GPIO Configuration
     PA2     ------> TIM15_CH1
     */
-    HAL_GPIO_DeInit(GPIOA, GPIO_PIN_2);
+    HAL_GPIO_DeInit(IMD_M_GPIO_Port, IMD_M_Pin);
 
+    /* TIM15 interrupt DeInit */
+    HAL_NVIC_DisableIRQ(TIM1_BRK_TIM15_IRQn);
   /* USER CODE BEGIN TIM15_MspDeInit 1 */
 
   /* USER CODE END TIM15_MspDeInit 1 */
diff --git a/Core/Src/stm32f3xx_it.c b/Core/Src/stm32f3xx_it.c
index 2c26531..ee4576d 100644
--- a/Core/Src/stm32f3xx_it.c
+++ b/Core/Src/stm32f3xx_it.c
@@ -56,6 +56,7 @@
 
 /* External variables --------------------------------------------------------*/
 extern CAN_HandleTypeDef hcan;
+extern TIM_HandleTypeDef htim15;
 /* USER CODE BEGIN EV */
 
 /* USER CODE END EV */
@@ -217,6 +218,20 @@ void USB_LP_CAN_RX0_IRQHandler(void)
   /* USER CODE END USB_LP_CAN_RX0_IRQn 1 */
 }
 
+/**
+  * @brief This function handles TIM1 break and TIM15 interrupts.
+  */
+void TIM1_BRK_TIM15_IRQHandler(void)
+{
+  /* USER CODE BEGIN TIM1_BRK_TIM15_IRQn 0 */
+
+  /* USER CODE END TIM1_BRK_TIM15_IRQn 0 */
+  HAL_TIM_IRQHandler(&htim15);
+  /* USER CODE BEGIN TIM1_BRK_TIM15_IRQn 1 */
+
+  /* USER CODE END TIM1_BRK_TIM15_IRQn 1 */
+}
+
 /* USER CODE BEGIN 1 */
 
 /* USER CODE END 1 */
diff --git a/STM32Make.make b/STM32Make.make
index 9e78481..ed043ae 100644
--- a/STM32Make.make
+++ b/STM32Make.make
@@ -38,6 +38,7 @@ BUILD_DIR = build
 C_SOURCES =  \
 Core/Lib/can-halal/can-halal.c \
 Core/Src/can.c \
+Core/Src/imd_monitoring.c \
 Core/Src/main.c \
 Core/Src/shunt_monitoring.c \
 Core/Src/slave_monitoring.c \
diff --git a/ams-master-23.ioc b/ams-master-23.ioc
index 50367be..5b8b3a3 100644
--- a/ams-master-23.ioc
+++ b/ams-master-23.ioc
@@ -86,6 +86,7 @@ NVIC.PendSV_IRQn=true\:0\:0\:false\:false\:true\:false\:false\:false
 NVIC.PriorityGroup=NVIC_PRIORITYGROUP_4
 NVIC.SVCall_IRQn=true\:0\:0\:false\:false\:true\:false\:false\:false
 NVIC.SysTick_IRQn=true\:15\:0\:false\:false\:true\:false\:true\:false
+NVIC.TIM1_BRK_TIM15_IRQn=true\:0\:0\:false\:false\:true\:true\:true\:true
 NVIC.USB_LP_CAN_RX0_IRQn=true\:0\:0\:false\:false\:true\:true\:true\:true
 NVIC.UsageFault_IRQn=true\:0\:0\:false\:false\:true\:false\:false\:false
 PA0.GPIOParameters=GPIO_Label
@@ -113,6 +114,8 @@ PA14.Mode=Trace_Asynchronous_SW
 PA14.Signal=SYS_JTCK-SWCLK
 PA15.Mode=I2C
 PA15.Signal=I2C1_SCL
+PA2.GPIOParameters=GPIO_Label
+PA2.GPIO_Label=IMD_M
 PA2.Locked=true
 PA2.Signal=S_TIM15_CH1
 PA3.GPIOParameters=GPIO_Label
@@ -237,7 +240,7 @@ ProjectManager.StackSize=0x400
 ProjectManager.TargetToolchain=Makefile
 ProjectManager.ToolChainLocation=
 ProjectManager.UnderRoot=false
-ProjectManager.functionlistsort=1-SystemClock_Config-RCC-false-HAL-false,2-MX_GPIO_Init-GPIO-false-HAL-true,3-MX_ADC2_Init-ADC2-false-HAL-true,4-MX_CAN_Init-CAN-false-HAL-true,5-MX_USART1_UART_Init-USART1-false-HAL-true
+ProjectManager.functionlistsort=1-SystemClock_Config-RCC-false-HAL-false,2-MX_GPIO_Init-GPIO-false-HAL-true,3-MX_ADC2_Init-ADC2-false-HAL-true,4-MX_CAN_Init-CAN-false-HAL-true,5-MX_USART1_UART_Init-USART1-false-HAL-true,6-MX_I2C1_Init-I2C1-false-HAL-true,7-MX_TIM15_Init-TIM15-false-HAL-true
 RCC.ADC12outputFreq_Value=16000000
 RCC.AHBFreq_Value=16000000
 RCC.APB1Freq_Value=16000000
@@ -274,6 +277,8 @@ RCC.USBFreq_Value=16000000
 RCC.VCOOutput2Freq_Value=4000000
 SH.S_TIM15_CH1.0=TIM15_CH1,PWM_Input_1
 SH.S_TIM15_CH1.ConfNb=1
+TIM15.IPParameters=Prescaler
+TIM15.Prescaler=16000-1
 USART1.IPParameters=VirtualMode-Asynchronous
 USART1.VirtualMode-Asynchronous=VM_ASYNC
 VP_SYS_VS_Systick.Mode=SysTick