try that

selfdrive/boardd/boardd.cc

@@ -135,7 +135,7 @@ bool safety_setter_thread(std::vector<Panda *> pandas) {
         pandas[i]->set_safety_model(cereal::CarParams::SafetyModel::ELM327, safety_param);
       }
       p.remove("ObdMultiplexingRequested", obd_multiplexing_requested);
-//      p.putBool("ObdMultiplexingEnabled", obd_multiplexing_requested);
+      p.putBool("ObdMultiplexingEnabled", obd_multiplexing_requested);
     }
 
     if (p.getBool("FirmwareQueryDone")) {

selfdrive/car/fw_versions.py

@@ -236,9 +236,9 @@ def get_fw_versions_ordered(logcan, sendcan, ecu_rx_addrs, timeout=0.1, num_pand
 def set_obd_multiplexing(params, obd_multiplexing):
   cloudlog.warning(f"Setting OBD multiplexing: {obd_multiplexing}")
   # Remove response param that boardd writes to block on it
-  params.remove("ObdMultiplexingDisabled")
+  params.remove("ObdMultiplexingEnabled")
   params.put_bool("ObdMultiplexingRequested", obd_multiplexing)
-  params.get_bool("ObdMultiplexingDisabled", block=True)
+  params.get_bool("ObdMultiplexingEnabled", block=True)
   cloudlog.warning(f"OBD multiplexing set successfully")