diff --git a/command/modbus_test.go b/command/modbus_test.go
index 0dda97c..62b7f72 100644
--- a/command/modbus_test.go
+++ b/command/modbus_test.go
@@ -12,7 +12,7 @@ func TestModbusValidateResponse(t *testing.T) {
 	validResponseWithExtraBytes := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 11, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 214, 1, 2, 3}
 	invalidReadLengthResponse := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 213}
 	invalidChecksumResponse := []byte{170, 85, 247, 3, 250, 22, 7, 15, 17, 46, 24, 11, 243, 0, 83, 0, 0, 9, 243, 9, 53, 0, 41, 0, 0, 3, 198, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 2, 9, 114, 0, 144, 19, 136, 0, 0, 13, 182, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 255, 255, 255, 255, 255, 255, 127, 255, 255, 255, 0, 1, 0, 0, 13, 182, 0, 0, 11, 153, 127, 255, 255, 255, 255, 255, 255, 255, 9, 112, 0, 5, 19, 136, 0, 1, 0, 0, 0, 0, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 2, 29, 128, 0, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 29, 0, 2, 2, 169, 127, 255, 2, 20, 1, 0, 14, 181, 255, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 33, 0, 1, 255, 255, 0, 0, 0, 0, 0, 0, 34, 145, 0, 0, 1, 100, 0, 0, 34, 139, 0, 0, 1, 52, 1, 96, 0, 0, 0, 0, 0, 0, 0, 0, 13, 73, 0, 126, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 64, 0, 0, 0, 2, 8, 64, 71, 0, 3, 0, 0, 255, 255, 147, 213}
-	failureCodeResponse := []byte{170, 85, 0, 0, 1, 176}
+	failureCodeResponse := []byte{170, 85, 0, 0, 2, 240, 1}
 
 	testCases := []struct {
 		name    string
@@ -36,7 +36,7 @@ func TestModbusValidateResponse(t *testing.T) {
 		{
 			name:    "failure code rcvd",
 			resp:    failureCodeResponse,
-			wantErr: "command failed with code: 1, error: FailureCodeIllegalFunction",
+			wantErr: "command failed with code: 2, error: FailureCodeIllegalDataAddress",
 		},
 		{
 			name: "valid response with extra bytes",