2002 jeep liberty error code 18 .what does it mean on 2002 Jeep Liberty

Was traveling about 70 miles hr and took exit when I came to stop it didn't down shift right away.Now I have to put it in 1st manually for it to go and now it won't shift in to over drive.Put meter on it and it comes up with error code 18 .No one seems to know what it means????

Asked by for the 2002 Jeep Liberty
the code has to have letters in frt of it,recheck codes and post.
1 more answer
Check on Auto Zone web site or Allpar.com. Both list all engine trouble codes and description.