diff --git a/java_console/io/src/main/java/com/rusefi/io/can/IsoTpCanDecoder.java b/java_console/io/src/main/java/com/rusefi/io/can/IsoTpCanDecoder.java
index b23ef4d0be..170443487f 100644
--- a/java_console/io/src/main/java/com/rusefi/io/can/IsoTpCanDecoder.java
+++ b/java_console/io/src/main/java/com/rusefi/io/can/IsoTpCanDecoder.java
@@ -1,9 +1,18 @@
 package com.rusefi.io.can;
 
+import com.devexperts.logging.Logging;
+import com.rusefi.io.IoStream;
+
 import java.util.Arrays;
 
 // CAN multiframe decoder state
 class IsoTpCanDecoder {
+    private static Logging log = Logging.getLogging(IsoTpCanDecoder.class);
+
+    static {
+        log.configureDebugEnabled(false);
+    }
+
     private final static int ISO_TP_FRAME_FLOW_CONTROL = 3;
     final static int ISO_TP_FRAME_SINGLE = 0;
     final static int ISO_TP_FRAME_FIRST = 1;
@@ -14,7 +23,8 @@ class IsoTpCanDecoder {
 
     public byte[] decodePacket(byte[] data) throws Exception {
         int frameType = (data[0] >> 4) & 0xf;
-        int numBytesAvailable, frameIdx;
+        int numBytesAvailable;
+        int frameIdx;
         int dataOffset;
         switch (frameType) {
             case ISO_TP_FRAME_SINGLE:
@@ -24,8 +34,11 @@ class IsoTpCanDecoder {
                 break;
             case ISO_TP_FRAME_FIRST:
                 this.waitingForNumBytes = ((data[0] & 0xf) << 8) | data[1];
+                if (log.debugEnabled())
+                    log.debug("Total expected: " + waitingForNumBytes);
                 this.waitingForFrameIndex = 1;
                 numBytesAvailable = Math.min(this.waitingForNumBytes, 6);
+                waitingForNumBytes -= numBytesAvailable;
                 dataOffset = 2;
                 break;
             case ISO_TP_FRAME_CONSECUTIVE:
@@ -36,13 +49,18 @@ class IsoTpCanDecoder {
                 this.waitingForFrameIndex = (this.waitingForFrameIndex + 1) & 0xf;
                 numBytesAvailable = Math.min(this.waitingForNumBytes, 7);
                 dataOffset = 1;
+                waitingForNumBytes -= numBytesAvailable;
+                if (log.debugEnabled())
+                    log.debug("ISO_TP_FRAME_CONSECUTIVE Got " + numBytesAvailable + ", still expecting: " + waitingForNumBytes);
                 break;
             case ISO_TP_FRAME_FLOW_CONTROL:
                 throw new Exception("ISO_TP_FRAME_FLOW_CONTROL: should we just ignore the FC frame?");
             default:
                 throw new Exception("Unknown frame type");
         }
-
-        return Arrays.copyOfRange(data, dataOffset, dataOffset + numBytesAvailable);
+        byte[] bytes = Arrays.copyOfRange(data, dataOffset, dataOffset + numBytesAvailable);
+        if (log.debugEnabled())
+            log.debug(numBytesAvailable + " bytes(s) arrived in this packet:" + IoStream.printHexBinary(bytes));
+        return bytes;
     }
 }
diff --git a/java_console/io/src/test/java/com/rusefi/binaryprotocol/test/Elm327Sandbox.java b/java_console/io/src/test/java/com/rusefi/binaryprotocol/test/Elm327Sandbox.java
index bcb7187655..a56114e18a 100644
--- a/java_console/io/src/test/java/com/rusefi/binaryprotocol/test/Elm327Sandbox.java
+++ b/java_console/io/src/test/java/com/rusefi/binaryprotocol/test/Elm327Sandbox.java
@@ -1,6 +1,8 @@
 package com.rusefi.binaryprotocol.test;
 
 import com.rusefi.binaryprotocol.BinaryProtocol;
+import com.rusefi.binaryprotocol.IncomingDataBuffer;
+import com.rusefi.config.generated.Fields;
 import com.rusefi.io.IoStream;
 import com.rusefi.io.can.Elm327Connector;
 import com.rusefi.io.serial.BaudRateHolder;
@@ -19,10 +21,41 @@ public class Elm327Sandbox {
 
         IoStream tsStream = connector.getTsStream();
 
-        String signature = BinaryProtocol.getSignature(tsStream);
-        System.out.println("Got " + signature + " signature via CAN/ELM327");
+        IncomingDataBuffer dataBuffer = tsStream.getDataBuffer();
+        System.out.println("Hello new connection " + dataBuffer.getPendingCount());
 
-        String signature2 = BinaryProtocol.getSignature(tsStream);
-        System.out.println("Got " + signature2 + " signature via CAN/ELM327");
+        runFcommand("First time", tsStream);
+        whyDoWeNeedToSleepBetweenCommands();
+
+        runFcommand("Second time", tsStream);
+        whyDoWeNeedToSleepBetweenCommands();
+
+        {
+            String signature = BinaryProtocol.getSignature(tsStream);
+            System.out.println("Got " + signature + " signature via CAN/ELM327");
+        }
+
+        whyDoWeNeedToSleepBetweenCommands();
+
+        {
+            String signature = BinaryProtocol.getSignature(tsStream);
+            System.out.println("Let's do it again! Got " + signature + " signature via CAN/ELM327");
+        }
+    }
+
+    private static void runFcommand(String prefix, IoStream tsStream) throws IOException {
+        IncomingDataBuffer dataBuffer = tsStream.getDataBuffer();
+        tsStream.sendPacket(new byte[]{Fields.TS_COMMAND_F});
+        byte[] fResponse = new byte[3];
+        dataBuffer.waitForBytes("hello", System.currentTimeMillis(), fResponse.length);
+        dataBuffer.getData(fResponse);
+        System.out.println(prefix + " Got F response " + IoStream.printHexBinary(fResponse));
+    }
+
+    /**
+     * TODO: HUH? what's that about?!
+     */
+    private static void whyDoWeNeedToSleepBetweenCommands() throws InterruptedException {
+        Thread.sleep(200);
     }
 }