If you want to save the previous pageName via DTM without a Plugin (getPreviousValue), you can use Session Storage. Two Pageload Rules are needed.

previous_pageName_session_storage

[Adobe Analytics|DTM] Previous pageName
If you want to save the previous pageName via DTM without a Plugin (getPreviousValue), you can use Session Storage. Two Pageload Rules are needed.

First PLR:
- Trigger Rule at “DOM Ready”
- Rule Condition: Path “.*” (regex enabled)
- Custom Code “None-Sequential Javascript”:

if(typeof(Storage) != "undefined") {
  if (typeof(s) !== "undefined") {
    sessionStorage.pagename = s.pageName;
  }
}
Second PLR:
- Trigger Rule at “Bottom of Page”
- Rule Condition: Path “.*” (regex enabled)
- Rule Condition: Custom:

if(typeof(Storage) !== "undefined") { 
  if(typeof(sessionStorage.getItem("pagename")) != "undefined") { 
    var prevPageName = sessionStorage.getItem("pagename");
    _satellite.setVar("previousPage",prevPageName);
    return true;
  }
}
- Adobe Analytics: prop2 set as %previousPage%

http://apastebin.tumblr.com/post/139627646180/adobe-analytics-dtm-previous-pagename