diff --git a/openpilot/common/params_keys.h b/openpilot/common/params_keys.h
index 3c5f30ab3d..6b6328df58 100644
--- a/openpilot/common/params_keys.h
+++ b/openpilot/common/params_keys.h
@@ -132,6 +132,7 @@ inline static std::unordered_map<std::string, ParamKeyAttributes> keys = {
     {"UptimeOnroad", {PERSISTENT, FLOAT, "0.0"}},
     {"ChestnutActive", {CLEAR_ON_MANAGER_START | CLEAR_ON_OFFROAD_TRANSITION | CLEAR_ON_IGNITION_ON, BOOL}},
     {"ChestnutLoading", {CLEAR_ON_MANAGER_START | CLEAR_ON_OFFROAD_TRANSITION | CLEAR_ON_IGNITION_ON, BOOL}},
+    {"AuxPowerSave", {PERSISTENT | BACKUP, BOOL}},
     {"Version", {PERSISTENT, STRING}},
 
     // --- sunnypilot params --- //
diff --git a/openpilot/selfdrive/ui/ui_state.py b/openpilot/selfdrive/ui/ui_state.py
index 4d93e1aacb..124852e4ba 100644
--- a/openpilot/selfdrive/ui/ui_state.py
+++ b/openpilot/selfdrive/ui/ui_state.py
@@ -220,6 +220,7 @@ class UIState(UIStateSP):
                              ChestnutState.UNCOMPILED if detected else ChestnutState.DISCONNECTED)
       return
 
+    self.chestnut_present = self.chestnut_present or detected
     model_seen = self.sm.recv_frame["modelV2"] > self.started_frame
     if not self.chestnut_present:
       self.chestnut_state = ChestnutState.DISCONNECTED
diff --git a/openpilot/sunnypilot/sunnylink/settings_ui.json b/openpilot/sunnypilot/sunnylink/settings_ui.json
index 63bf342fcb..f0cbc07837 100644
--- a/openpilot/sunnypilot/sunnylink/settings_ui.json
+++ b/openpilot/sunnypilot/sunnylink/settings_ui.json
@@ -1675,6 +1675,12 @@
               "widget": "toggle",
               "title": "Onroad Uploads"
             },
+            {
+              "key": "AuxPowerSave",
+              "widget": "toggle",
+              "title": "Disable Aux Port When Offroad",
+              "description": "Power off the aux USB-C port while offroad to save power. It powers back on automatically when you go onroad."
+            },
             {
               "key": "MaxTimeOffroad",
               "widget": "option",
diff --git a/openpilot/sunnypilot/sunnylink/settings_ui_src/pages/device.yaml b/openpilot/sunnypilot/sunnylink/settings_ui_src/pages/device.yaml
index bf5f7883ab..d519a1f9b9 100644
--- a/openpilot/sunnypilot/sunnylink/settings_ui_src/pages/device.yaml
+++ b/openpilot/sunnypilot/sunnylink/settings_ui_src/pages/device.yaml
@@ -30,6 +30,10 @@ sections:
   - key: OnroadUploads
     widget: toggle
     title: Onroad Uploads
+  - key: AuxPowerSave
+    widget: toggle
+    title: Disable Aux Port When Offroad
+    description: Power off the aux USB-C port while offroad to save power. It powers back on automatically when you go onroad.
   - key: MaxTimeOffroad
     widget: option
     title: Max Time Offroad
diff --git a/openpilot/system/hardware/hardwared.py b/openpilot/system/hardware/hardwared.py
index dd9c92269b..e6e8486a1e 100755
--- a/openpilot/system/hardware/hardwared.py
+++ b/openpilot/system/hardware/hardwared.py
@@ -21,6 +21,7 @@ from openpilot.selfdrive.selfdrived.alertmanager import set_offroad_alert
 from openpilot.common.hardware import HARDWARE, COMMA_HARDWARE
 from openpilot.common.basedir import BASEDIR
 from openpilot.common.hardware.usb import CHESTNUT_FW_VERSION, CHESTNUT_ROM_USB_IDS, CHESTNUT_USB_IDS, get_usb_state, get_usb_topology, set_usb_state
+from openpilot.system.hardware.chestnut.flash import VBUS_PATH
 from openpilot.common.linux import LinuxSystemStats
 from openpilot.system.loggerd.config import get_available_percent
 from openpilot.common.swaglog import cloudlog
@@ -49,6 +50,10 @@ class Chestnut:
     self.attempts = 0
     self.last_attempt = 0.
     self.flashed = False
+    self.vbus_on = None
+    self.params = Params()
+    self.powersave = False
+    self.last_offroad = None
 
   def flash(self) -> None:
     ret = subprocess.run(["sudo", sys.executable, os.path.join(BASEDIR, "openpilot/system/hardware/chestnut/flash.py"), CHESTNUT_FW_VERSION],
@@ -56,9 +61,19 @@ class Chestnut:
     cloudlog.event("chestnut flash done", returncode=ret.returncode, output=ret.stdout[-1000:], error=ret.returncode != 0)
     self.flashed = ret.returncode == 0
 
+  def set_vbus(self, on: bool) -> None:
+    if on == self.vbus_on:
+      return
+    subprocess.run(["sudo", "tee", VBUS_PATH], input=b"1" if on else b"0", stdout=subprocess.DEVNULL, check=False)
+    self.vbus_on = on
+
   def update(self, offroad: bool, usb_state: list[dict]) -> None:
     mismatch = any((d["vendorId"], d["productId"]) in CHESTNUT_USB_IDS + CHESTNUT_ROM_USB_IDS and
                    d["product"] != f"custom {CHESTNUT_FW_VERSION}-CLEAN" for d in usb_state)
+    if offroad != self.last_offroad:
+      self.powersave = self.params.get_bool("AuxPowerSave")
+      self.last_offroad = offroad
+    self.set_vbus((not offroad or mismatch) or not self.powersave)
     if not mismatch:
       self.flashed = False
       return