diff --git a/selfdrive/debug/can_print_changes.py b/selfdrive/debug/can_print_changes.py
index 7e49487b59ffce..2f31118e41a109 100755
--- a/selfdrive/debug/can_print_changes.py
+++ b/selfdrive/debug/can_print_changes.py
@@ -7,16 +7,19 @@
 import cereal.messaging as messaging
 from tools.lib.logreader import logreader_from_route_or_segment
 
+RED = '\033[91m'
+CLEAR = '\033[0m'
 
-def update(msgs, bus, low_to_high, high_to_low, quiet=False):
+def update(msgs, bus, dat, low_to_high, high_to_low, quiet=False):
   for x in msgs:
     if x.which() != 'can':
       continue
 
     for y in x.can:
       if y.src == bus:
-        i = int.from_bytes(y.dat, byteorder='big')
+        dat[y.address] = y.dat
 
+        i = int.from_bytes(y.dat, byteorder='big')
         l_h = low_to_high[y.address]
         h_l = high_to_low[y.address]
 
@@ -34,35 +37,51 @@ def update(msgs, bus, low_to_high, high_to_low, quiet=False):
 
 
 def can_printer(bus=0, init_msgs=None, new_msgs=None):
-  logcan = messaging.sub_sock('can')
+  logcan = messaging.sub_sock('can', timeout=10)
 
+  dat = defaultdict(int)
   low_to_high = defaultdict(int)
   high_to_low = defaultdict(int)
 
   if init_msgs is not None:
-    update(init_msgs, bus, low_to_high, high_to_low, quiet=True)
+    update(init_msgs, bus, dat, low_to_high, high_to_low, quiet=True)
+
+  low_to_high_init = low_to_high.copy()
+  high_to_low_init = high_to_low.copy()
 
   if new_msgs is not None:
-    update(new_msgs, bus, low_to_high, high_to_low)
+    update(new_msgs, bus, dat, low_to_high, high_to_low)
   else:
     # Live mode
-    while 1:
-      can_recv = messaging.drain_sock(logcan, wait_for_one=True)
-      update(can_recv, bus, low_to_high, high_to_low)
+    try:
+      while 1:
+        can_recv = messaging.drain_sock(logcan)
+        update(can_recv, bus, dat, low_to_high, high_to_low)
+        time.sleep(0.02)
+    except KeyboardInterrupt:
+      pass
+
+  print("\n\n")
+  for addr in sorted(dat.keys()):
+    init = low_to_high_init[addr] & high_to_low_init[addr]
+    now = low_to_high[addr] & high_to_low[addr]
+    d = now & ~init
+    if d == 0:
+      continue
+    b = d.to_bytes(len(dat[addr]), byteorder='big')
+    byts = ''.join([(c if c == '0' else f'{RED}{c}{CLEAR}') for c in str(binascii.hexlify(b))[2:-1]])
+    print(f"{hex(addr).ljust(6)}({str(addr).ljust(4)})", byts)
 
 
 if __name__ == "__main__":
   desc = """Collects messages and prints when a new bit transition is observed.
   This is very useful to find signals based on user triggered actions, such as blinkers and seatbelt.
   Leave the script running until no new transitions are seen, then perform the action."""
-
   parser = argparse.ArgumentParser(description=desc,
                                    formatter_class=argparse.ArgumentDefaultsHelpFormatter)
-
   parser.add_argument("--bus", type=int, help="CAN bus to print out", default=0)
-
-  parser.add_argument("init", type=str, help="Route or segment to initialize with")
-  parser.add_argument("comp", type=str, help="Route or segment to compare against init")
+  parser.add_argument("init", type=str, nargs='?', help="Route or segment to initialize with")
+  parser.add_argument("comp", type=str, nargs='?', help="Route or segment to compare against init")
 
   args = parser.parse_args()