diff --git a/src/main/java/com/romraider/io/j2534/api/J2534ConnectionISO15765.java b/src/main/java/com/romraider/io/j2534/api/J2534ConnectionISO15765.java
index 95be16c8..badfc8da 100644
--- a/src/main/java/com/romraider/io/j2534/api/J2534ConnectionISO15765.java
+++ b/src/main/java/com/romraider/io/j2534/api/J2534ConnectionISO15765.java
@@ -55,7 +55,7 @@ public final class J2534ConnectionISO15765 implements ConnectionManager {
     @Override
     public void open(byte[] start, byte[] stop) {
         checkNotNull(start, "start");
-        checkNotNull(start, "stop");
+        checkNotNull(stop, "stop");
         this.stopRequest = stop;
         LOGGER.debug(String.format("Start Diagnostics Request  ---> %s",
                 asHex(start)));
@@ -94,12 +94,14 @@ public final class J2534ConnectionISO15765 implements ConnectionManager {
 
     @Override
     public void close() {
-        LOGGER.debug(String.format("Stop Diagnostics Request  ---> %s",
-                asHex(stopRequest)));
-        api.writeMsg(channelId, stopRequest, timeout, TxFlags.ISO15765_FRAME_PAD);
-        final byte[] response = api.readMsg(channelId, 1, timeout);
-        LOGGER.debug(String.format("Stop Diagnostics Response <--- %s",
-                asHex(response)));
+        if (stopRequest != null) {  // OBD has no open or close procedure
+            LOGGER.debug(String.format("Stop Diagnostics Request  ---> %s",
+                    asHex(stopRequest)));
+            api.writeMsg(channelId, stopRequest, timeout, TxFlags.ISO15765_FRAME_PAD);
+            final byte[] response = api.readMsg(channelId, 1, timeout);
+            LOGGER.debug(String.format("Stop Diagnostics Response <--- %s",
+                    asHex(response)));
+        }
         stopFcFilter();
         disconnectChannel();
         closeDevice();