diff --git a/selfdrive/car/car_helpers.py b/selfdrive/car/car_helpers.py
index 1ad584de26..652862de47 100644
--- a/selfdrive/car/car_helpers.py
+++ b/selfdrive/car/car_helpers.py
@@ -1,5 +1,5 @@
 import os
-from typing import Dict, List
+from typing import Callable, Dict, List, Optional, Tuple
 
 from cereal import car
 from common.params import Params
@@ -77,6 +77,46 @@ interface_names = _get_interface_names()
 interfaces = load_interfaces(interface_names)
 
 
+def can_fingerprint(next_can: Callable) -> Tuple[Optional[str], Dict[int, dict]]:
+  finger = gen_empty_fingerprint()
+  candidate_cars = {i: all_legacy_fingerprint_cars() for i in [0, 1]}  # attempt fingerprint on both bus 0 and 1
+  frame = 0
+  car_fingerprint = None
+  done = False
+
+  while not done:
+    a = next_can()
+
+    for can in a.can:
+      # The fingerprint dict is generated for all buses, this way the car interface
+      # can use it to detect a (valid) multipanda setup and initialize accordingly
+      if can.src < 128:
+        if can.src not in finger:
+          finger[can.src] = {}
+        finger[can.src][can.address] = len(can.dat)
+
+      for b in candidate_cars:
+        # Ignore extended messages and VIN query response.
+        if can.src == b and can.address < 0x800 and can.address not in (0x7df, 0x7e0, 0x7e8):
+          candidate_cars[b] = eliminate_incompatible_cars(can, candidate_cars[b])
+
+    # if we only have one car choice and the time since we got our first
+    # message has elapsed, exit
+    for b in candidate_cars:
+      if len(candidate_cars[b]) == 1 and frame > FRAME_FINGERPRINT:
+        # fingerprint done
+        car_fingerprint = candidate_cars[b][0]
+
+    # bail if no cars left or we've been waiting for more than 2s
+    failed = (all(len(cc) == 0 for cc in candidate_cars.values()) and frame > FRAME_FINGERPRINT) or frame > 200
+    succeeded = car_fingerprint is not None
+    done = failed or succeeded
+
+    frame += 1
+
+  return car_fingerprint, finger
+
+
 # **** for use live only ****
 def fingerprint(logcan, sendcan, num_pandas):
   fixed_fingerprint = os.environ.get('FINGERPRINT', "")
@@ -125,44 +165,10 @@ def fingerprint(logcan, sendcan, num_pandas):
   set_obd_multiplexing(params, False)
   params.put_bool("FirmwareQueryDone", True)
 
-  finger = gen_empty_fingerprint()
-  candidate_cars = {i: all_legacy_fingerprint_cars() for i in [0, 1]}  # attempt fingerprint on both bus 0 and 1
-  frame = 0
-  car_fingerprint = None
-  done = False
-
-  # drain CAN socket so we always get the latest messages
+  # CAN fingerprint
+  # drain CAN socket so we get the latest messages
   messaging.drain_sock_raw(logcan)
-
-  while not done:
-    a = get_one_can(logcan)
-
-    for can in a.can:
-      # The fingerprint dict is generated for all buses, this way the car interface
-      # can use it to detect a (valid) multipanda setup and initialize accordingly
-      if can.src < 128:
-        if can.src not in finger:
-          finger[can.src] = {}
-        finger[can.src][can.address] = len(can.dat)
-
-      for b in candidate_cars:
-        # Ignore extended messages and VIN query response.
-        if can.src == b and can.address < 0x800 and can.address not in (0x7df, 0x7e0, 0x7e8):
-          candidate_cars[b] = eliminate_incompatible_cars(can, candidate_cars[b])
-
-    # if we only have one car choice and the time since we got our first
-    # message has elapsed, exit
-    for b in candidate_cars:
-      if len(candidate_cars[b]) == 1 and frame > FRAME_FINGERPRINT:
-        # fingerprint done
-        car_fingerprint = candidate_cars[b][0]
-
-    # bail if no cars left or we've been waiting for more than 2s
-    failed = (all(len(cc) == 0 for cc in candidate_cars.values()) and frame > FRAME_FINGERPRINT) or frame > 200
-    succeeded = car_fingerprint is not None
-    done = failed or succeeded
-
-    frame += 1
+  car_fingerprint, finger = can_fingerprint(lambda: get_one_can(logcan))
 
   exact_match = True
   source = car.CarParams.FingerprintSource.can