diff --git a/python/uds.py b/python/uds.py
index 5e2f50d9..9fd179cc 100644
--- a/python/uds.py
+++ b/python/uds.py
@@ -556,15 +556,16 @@ def get_rx_addr_for_tx_addr(tx_addr, rx_offset=0x8):
 
 
 class UdsClient():
-  def __init__(self, panda, tx_addr: int, rx_addr: int = None, bus: int = 0, timeout: float = 1, debug: bool = False,
-               tx_timeout: float = 1, response_pending_timeout: float = 10):
+  def __init__(self, panda, tx_addr: int, rx_addr: int = None, bus: int = 0, sub_addr: int = None, timeout: float = 1,
+               debug: bool = False, tx_timeout: float = 1, response_pending_timeout: float = 10):
     self.bus = bus
     self.tx_addr = tx_addr
     self.rx_addr = rx_addr if rx_addr is not None else get_rx_addr_for_tx_addr(tx_addr)
+    self.sub_addr = sub_addr
     self.timeout = timeout
     self.debug = debug
     can_send_with_timeout = partial(panda.can_send, timeout=int(tx_timeout*1000))
-    self._can_client = CanClient(can_send_with_timeout, panda.can_recv, self.tx_addr, self.rx_addr, self.bus, debug=self.debug)
+    self._can_client = CanClient(can_send_with_timeout, panda.can_recv, self.tx_addr, self.rx_addr, self.bus, self.sub_addr, debug=self.debug)
     self.response_pending_timeout = response_pending_timeout
 
   # generic uds request
@@ -576,7 +577,8 @@ class UdsClient():
       req += data
 
     # send request, wait for response
-    isotp_msg = IsoTpMessage(self._can_client, timeout=self.timeout, debug=self.debug)
+    max_len = 8 if self.sub_addr is None else 7
+    isotp_msg = IsoTpMessage(self._can_client, timeout=self.timeout, debug=self.debug, max_len=max_len)
     isotp_msg.send(req)
     response_pending = False
     while True: