diff --git a/firmware/can.cpp b/firmware/can.cpp
index ecd336e..1f50ea6 100644
--- a/firmware/can.cpp
+++ b/firmware/can.cpp
@@ -61,8 +61,8 @@ void CanRxThread(void*)
             SetBatteryVoltage(vbatt);
 
             // data1 contains heater enable bit
-            // TODO use this
-            //bool heaterEnabled = (frame.data8[1] & 0x1) == 0x1;
+            bool heaterAllowed = (frame.data8[1] & 0x1) == 0x1;
+            SetHeaterAllowed(heaterAllowed);
         }
         // If it's a bootloader entry request, reboot to the bootloader!
         else if (frame.DLC == 0 && frame.EID == 0xEF0'0000)
diff --git a/firmware/heater_control.cpp b/firmware/heater_control.cpp
index 5b2d68e..a53b8c8 100644
--- a/firmware/heater_control.cpp
+++ b/firmware/heater_control.cpp
@@ -20,11 +20,20 @@ enum class HeaterState
     Stopped,
 };
 
-int timeCounter = HEATER_PREHEAT_TIME / HEATER_CONTROL_PERIOD;
-float rampVoltage = 0;
+constexpr int preheatTimeCounter = HEATER_PREHEAT_TIME / HEATER_CONTROL_PERIOD;
+static int timeCounter = preheatTimeCounter;
+static float rampVoltage = 0;
+static bool heaterAllowed = false;
 
 static HeaterState GetNextState(HeaterState state, float sensorEsr)
 {
+    if (!heaterAllowed)
+    {
+        // ECU hasn't allowed preheat yet, reset timer, and force preheat state
+        timeCounter = preheatTimeCounter;
+        return HeaterState::Preheat;
+    }
+
     switch (state)
     {
         case HeaterState::Preheat:
@@ -187,3 +196,8 @@ void SetBatteryVoltage(float vbatt)
         batteryVoltage = vbatt;
     }
 }
+
+void SetHeaterAllowed(bool allowed)
+{
+    heaterAllowed = allowed;
+}
diff --git a/firmware/heater_control.h b/firmware/heater_control.h
index 0dc0959..9e413b3 100644
--- a/firmware/heater_control.h
+++ b/firmware/heater_control.h
@@ -5,3 +5,4 @@
 void StartHeaterControl();
 bool IsRunningClosedLoop();
 void SetBatteryVoltage(float vbatt);
+void SetHeaterAllowed(bool allowed);