diff --git a/tc/OBSW_TcService3.py b/tc/OBSW_TcService3.py
index d55d7f913a42f38dda524afb6c9ddb507dd7cb4e..1e96a21f5239dc05e100f1d28f206afba21307b8 100644
--- a/tc/OBSW_TcService3.py
+++ b/tc/OBSW_TcService3.py
@@ -6,12 +6,28 @@ Description: PUS Custom Service 8: Device Access, Native low-level commanding
 
 @author: R. Mueller
 """
+import struct
+from tc.OBSW_TcPacket import PUSTelecommand
 
 
 def packService3TestInto(tcQueue):
     tcQueue.put(("print", "Testing Service 3"))
     # adding custom defintion to hk using test pool variables
+    tcQueue.put(("print", "\r\nTesting Service 3: Adding custom definition"))
+    sid = bytearray([0x00, 0x00, 0x42, 0x00])
+    collectionInterval = struct.pack('>f', 3)
+    numberOfParameters = struct.pack('B', 5)
+    p1 = bytearray([0x01, 0x01, 0x01, 0x01])
+    p2 = bytearray([0x02, 0x02, 0x02, 0x02])
+    p3 = bytearray([0x03, 0x03, 0x03, 0x03])
+    p4 = bytearray([0x04, 0x04, 0x04, 0x04])
+    p5 = bytearray([0x05, 0x05, 0x05, 0x05])
+    hkDefinition = sid + collectionInterval + numberOfParameters + p1 + p2 + p3 + p4 + p5
+    command = PUSTelecommand(service=3, subservice=1, SSC=3010, data=hkDefinition)
+    tcQueue.put(command.packCommandTuple())
     # adding custom definition to diagnostics using test pool variables
+    command = PUSTelecommand(service=3, subservice=2, SSC=3010, data=hkDefinition)
+    tcQueue.put(command.packCommandTuple())
     # enable custom hk definition
     # enable custom diag definition
     # disable custom hk definition
@@ -32,3 +48,5 @@ def packService3TestInto(tcQueue):
     # delete custom diag definition
     # do some basic testing on predefined structs too
     # e.g. add one variable, change interval, report them....
+    tcQueue.put(("export", "log/tmtc_log_service3.txt"))
+    return tcQueue