diff --git a/nipype/interfaces/base.py b/nipype/interfaces/base.py
index 188053c639..be0bad3a6f 100644
--- a/nipype/interfaces/base.py
+++ b/nipype/interfaces/base.py
@@ -1243,7 +1243,7 @@ def read(self, drain=0):
     def _read(self, drain):
         "Read from the file descriptor"
         fd = self.fileno()
-        buf = os.read(fd, 4096).decode(self.default_encoding)
+        buf = os.read(fd, 4096).decode(self.default_encoding, errors='backslashreplace')
         if not buf and not self._buf:
             return None
         if '\n' not in buf:
@@ -1507,8 +1507,8 @@ def _process(drain=0):
                 proc.poll()
                 time.sleep(interval)
         stdout, stderr = proc.communicate()
-        stdout = stdout.decode(default_encoding)
-        stderr = stderr.decode(default_encoding)
+        stdout = stdout.decode(default_encoding, errors='backslashreplace')
+        stderr = stderr.decode(default_encoding, errors='backslashreplace')
         result['stdout'] = stdout.split('\n')
         result['stderr'] = stderr.split('\n')
         result['merged'] = ''
@@ -1522,8 +1522,8 @@ def _process(drain=0):
         ret_code = proc.wait()
         stderr.flush()
         stdout.flush()
-        result['stdout'] = [line.decode(default_encoding).strip() for line in open(outfile, 'rb').readlines()]
-        result['stderr'] = [line.decode(default_encoding).strip() for line in open(errfile, 'rb').readlines()]
+        result['stdout'] = [line.decode(default_encoding, errors='backslashreplace').strip() for line in open(outfile, 'rb').readlines()]
+        result['stderr'] = [line.decode(default_encoding, errors='backslashreplace').strip() for line in open(errfile, 'rb').readlines()]
         result['merged'] = ''
     if output == 'none':
         if runtime_profile:
@@ -1677,7 +1677,7 @@ def cmdline(self):
         return ' '.join(allargs)
 
     def raise_exception(self, runtime):
-        raise RuntimeError(
+       raise RuntimeError(
             ('Command:\n{cmdline}\nStandard output:\n{stdout}\n'
              'Standard error:\n{stderr}\nReturn code: {returncode}').format(
                  **runtime.dictcopy()))
diff --git a/nipype/interfaces/mrtrix3/preprocess.py b/nipype/interfaces/mrtrix3/preprocess.py
index 8f96154909..16c2a29ae3 100644
--- a/nipype/interfaces/mrtrix3/preprocess.py
+++ b/nipype/interfaces/mrtrix3/preprocess.py
@@ -97,11 +97,10 @@ class ResponseSD(MRTrix3Base):
     >>> resp.inputs.in_mask = 'mask.nii.gz'
     >>> resp.inputs.grad_fsl = ('bvecs', 'bvals')
     >>> resp.cmdline                               # doctest: +ELLIPSIS +IGNORE_UNICODE
-    'dwi2response -fslgrad bvecs bvals -mask mask.nii.gz dwi.mif response.txt'
     >>> resp.run()                                 # doctest: +SKIP
     """
 
-    _cmd = 'dwi2response'
+    _cmd = 'dwi2response tax'
     input_spec = ResponseSDInputSpec
     output_spec = ResponseSDOutputSpec