diff --git a/selfdrive/car/car_helpers.py b/selfdrive/car/car_helpers.py
index bd848b30a..413f905de 100644
--- a/selfdrive/car/car_helpers.py
+++ b/selfdrive/car/car_helpers.py
@@ -209,7 +209,8 @@ def get_car(logcan, sendcan, experimental_long_allowed, params, num_pandas=1, fr
   CP.fingerprintSource = source
   CP.fuzzyFingerprint = not exact_match
 
-  return get_car_interface(CP, FPCP), CP, FPCP
+  interface_instance = get_car_interface(CP, None)
+  return interface_instance, CP, FPCP
 
 def write_car_param(platform=MOCK.MOCK):
   params = Params()
diff --git a/selfdrive/car/gm/interface.py b/selfdrive/car/gm/interface.py
index cb1b1d4f7..abc58e309 100644
--- a/selfdrive/car/gm/interface.py
+++ b/selfdrive/car/gm/interface.py
@@ -98,6 +98,8 @@ class CarInterface(CarInterfaceBase):
     if PEDAL_MSG in fingerprint[0]:
       ret.enableGasInterceptor = True
       ret.safetyConfigs[0].safetyParam |= Panda.FLAG_GM_GAS_INTERCEPTOR
+      # When a pedal interceptor is present, always use normal longitudinal (block stock cruise)
+      experimental_long = False
 
     if candidate in EV_CAR:
       ret.transmissionType = TransmissionType.direct
diff --git a/selfdrive/car/interfaces.py b/selfdrive/car/interfaces.py
index 63eeabdef..49d43872a 100644
--- a/selfdrive/car/interfaces.py
+++ b/selfdrive/car/interfaces.py
@@ -218,9 +218,10 @@ class CarInterfaceBase(ABC):
     self.silent_steer_warning = True
     self.v_ego_cluster_seen = False
 
-    self.CS = CarState(CP, FPCP)
-    self.cp = self.CS.get_can_parser(CP, FPCP)
-    self.cp_cam = self.CS.get_cam_can_parser(CP, FPCP)
+    self.CS = CarState(CP, None)
+    fp = FPCP if FPCP is not None else getattr(self, "FPCP", None)
+    self.cp = self.CS.get_can_parser(CP, fp)
+    self.cp_cam = self.CS.get_cam_can_parser(CP, fp)
     self.cp_adas = self.CS.get_adas_can_parser(CP)
     self.cp_body = self.CS.get_body_can_parser(CP)
     self.cp_loopback = self.CS.get_loopback_can_parser(CP)