diff --git a/panda/board/drivers/gmlan_alt.h b/panda/board/drivers/gmlan_alt.h
index 6d4ba12b8..2f2e56805 100644
--- a/panda/board/drivers/gmlan_alt.h
+++ b/panda/board/drivers/gmlan_alt.h
@@ -122,7 +122,12 @@ int get_bit_message(char *out, CAN_FIFOMailBox_TypeDef *to_bang) {
   return len;
 }
 
+void TIM4_IRQ_Handler(void);
+
 void setup_timer4(void) {
+  // register interrupt
+  REGISTER_INTERRUPT(TIM4_IRQn, TIM4_IRQ_Handler, 40000U, FAULT_INTERRUPT_RATE_GMLAN)
+
   // setup
   register_set(&(TIM4->PSC), (48-1), 0xFFFFU);    // Tick on 1 us
   register_set(&(TIM4->CR1), TIM_CR1_CEN, 0x3FU); // Enable
@@ -236,7 +241,6 @@ void TIM4_IRQ_Handler(void) {
         gmlan_sendmax = -1;   // exit
       }
     }
-    TIM4->SR = 0;
   } else if (gmlan_alt_mode == GPIO_SWITCH) {
     if ((TIM4->SR & TIM_SR_UIF) && (gmlan_switch_below_timeout != -1)) {
       if ((can_timeout_counter == 0) && gmlan_switch_timeout_enable) {
@@ -259,10 +263,10 @@ void TIM4_IRQ_Handler(void) {
         }
       }
     }
-    TIM4->SR = 0;
   } else {
-    puts("invalid gmlan_alt_mode\n");
+    // Invalid GMLAN mode. Do not put a print statement here, way too fast to keep up with
   }
+  TIM4->SR = 0;
 }
 
 bool bitbang_gmlan(CAN_FIFOMailBox_TypeDef *to_bang) {
@@ -280,7 +284,6 @@ bool bitbang_gmlan(CAN_FIFOMailBox_TypeDef *to_bang) {
     set_gpio_mode(GPIOB, 13, MODE_OUTPUT);
 
     // 33kbps
-    REGISTER_INTERRUPT(TIM4_IRQn, TIM4_IRQ_Handler, 40000U, FAULT_INTERRUPT_RATE_GMLAN)
     setup_timer4();
   }
   return gmlan_send_ok;
diff --git a/panda/board/main.c b/panda/board/main.c
index a758bf705..8bc4ac78f 100644
--- a/panda/board/main.c
+++ b/panda/board/main.c
@@ -294,19 +294,11 @@ int usb_cb_control_msg(USB_Setup_TypeDef *setup, uint8_t *resp, bool hardwired)
       break;
     // **** 0xb0: set IR power
     case 0xb0:
-      if(power_save_status == POWER_SAVE_STATUS_DISABLED){
-        current_board->set_ir_power(setup->b.wValue.w);
-      } else {
-        puts("Setting IR power not allowed in power saving mode\n");
-      }
+      current_board->set_ir_power(setup->b.wValue.w);
       break;
     // **** 0xb1: set fan power
     case 0xb1:
-      if(power_save_status == POWER_SAVE_STATUS_DISABLED){
-        current_board->set_fan_power(setup->b.wValue.w);
-      } else {
-        puts("Setting fan power not allowed in power saving mode\n");
-      }
+      current_board->set_fan_power(setup->b.wValue.w);
       break;
     // **** 0xb2: get fan rpm
     case 0xb2:
@@ -716,6 +708,10 @@ void TIM1_BRK_TIM9_IRQ_Handler(void) {
       if (power_save_status != POWER_SAVE_STATUS_ENABLED) {
         set_power_save_state(POWER_SAVE_STATUS_ENABLED);
       }
+
+      // Also disable fan and IR when the heartbeat goes missing
+      current_board->set_fan_power(0U);
+      current_board->set_ir_power(0U);
     }
 
     // enter CDP mode when car starts to ensure we are charging a turned off EON
diff --git a/panda/board/power_saving.h b/panda/board/power_saving.h
index 3ee2170d7..f7e42371a 100644
--- a/panda/board/power_saving.h
+++ b/panda/board/power_saving.h
@@ -49,10 +49,9 @@ void set_power_save_state(int state) {
       set_gpio_output(GPIOA, 14, enable);
     }
 
-    // Switch off IR and fan when in power saving
+    // Switch off IR when in power saving
     if(!enable){
       current_board->set_ir_power(0U);
-      current_board->set_fan_power(0U);
     }   
 
     power_save_status = state;
diff --git a/panda/python/uds.py b/panda/python/uds.py
index 96d07e1a7..548f1bcce 100644
--- a/panda/python/uds.py
+++ b/panda/python/uds.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 import time
 import struct
+from collections import deque
 from typing import Callable, NamedTuple, Tuple, List
 from enum import IntEnum
 
@@ -275,11 +276,12 @@ class CanClient():
     self.rx = can_recv
     self.tx_addr = tx_addr
     self.rx_addr = rx_addr
+    self.rx_buff = deque()
     self.sub_addr = sub_addr
     self.bus = bus
     self.debug = debug
 
-  def _recv_filter(self, bus, addr):
+  def _recv_filter(self, bus: int, addr: int) -> bool:
     # handle functional addresses (switch to first addr to respond)
     if self.tx_addr == 0x7DF:
       is_response = addr >= 0x7E8 and addr <= 0x7EF
@@ -296,12 +298,12 @@ class CanClient():
         self.rx_addr = addr
     return bus == self.bus and addr == self.rx_addr
 
-  def recv(self, drain=False) -> List[bytes]:
-    msg_array = []
+  def _recv_buffer(self, drain: bool=False) -> None:
     while True:
       msgs = self.rx()
       if drain:
         if self.debug: print("CAN-RX: drain - {}".format(len(msgs)))
+        self.rx_buff.clear()
       else:
         for rx_addr, rx_ts, rx_data, rx_bus in msgs or []:
           if self._recv_filter(rx_bus, rx_addr) and len(rx_data) > 0:
@@ -313,15 +315,24 @@ class CanClient():
             if self.sub_addr is not None:
               rx_data = rx_data[1:]
 
-            msg_array.append(rx_data)
+            self.rx_buff.append(rx_data)
       # break when non-full buffer is processed
       if len(msgs) < 254:
-        return msg_array
+        return
+
+  def recv(self, drain: bool=False) -> List[bytes]:
+    # buffer rx messages in case two response messages are received at once
+    # (e.g. response pending and success/failure response)
+    self._recv_buffer(drain)
+    try:
+      while True:
+        yield self.rx_buff.popleft()
+    except IndexError:
+      pass # empty
 
   def send(self, msgs: List[bytes], delay: float=0) -> None:
-    first = True
-    for msg in msgs:
-      if delay and not first:
+    for i, msg in enumerate(msgs):
+      if delay and i != 0:
         if self.debug: print(f"CAN-TX: delay - {delay}")
         time.sleep(delay)
 
@@ -332,8 +343,9 @@ class CanClient():
       assert len(msg) <= 8
 
       self.tx(self.tx_addr, msg, self.bus)
-      first = False
-
+      # prevent rx buffer from overflowing on large tx
+      if i % 10 == 9:
+        self._recv_buffer()
 
 class IsoTpMessage():
   def __init__(self, can_client: CanClient, timeout: float=1, debug: bool=False, max_len: int=8):