diff --git a/selfdrive/car/tests/test_fw_fingerprint.py b/selfdrive/car/tests/test_fw_fingerprint.py
index 697aa41650..2a47c60bf3 100755
--- a/selfdrive/car/tests/test_fw_fingerprint.py
+++ b/selfdrive/car/tests/test_fw_fingerprint.py
@@ -53,6 +53,12 @@ class TestFwFingerprint(unittest.TestCase):
           for ecu in ecus.keys():
             self.assertNotIn(ecu[1], blacklisted_addrs, f'{car_model}: Blacklisted ecu: (Ecu.{ECU_NAME[ecu[0]]}, {hex(ecu[1])})')
 
+        elif CP.carName == "chrysler":
+          # Some HD trucks have a combined TCM and ECM
+          if CP.carFingerprint.startswith("RAM HD"):
+            for ecu in ecus.keys():
+              self.assertNotEqual(ecu[0], Ecu.transmission, f"{car_model}: Blacklisted ecu: (Ecu.{ECU_NAME[ecu[0]]}, {hex(ecu[1])})")
+
   def test_fw_request_ecu_whitelist(self):
     for brand in set(r.brand for r in REQUESTS):
       with self.subTest(brand=brand):