If your E-Z-GO PDS golf cart will only go forward but not go in reverse there are two things that might be wrong. One is a simple fix and the other is much more expensive to repair.
There are exceptions to this rule but for the most part you have one of two problems with your EZGO.
First check your PDS Forward and Reverse switch for any loose connections. If all the connections are good try swamping the top and bottom wires on the back of the F/R switch. If the problem reverses it’s self (You can now go backwards but not forwards) then you have a bad F/W switch. Just buy a new one from here (Forward and Reverse Switch) and install it in place of the old switch. You should be good to go and that should have solved the issue. Great, a cheap fix and happy days ahead!
If that did not fix your problem you likely have a bad controller. Not the cheap fix like above. EZGO PDS stock controllers have two sections inside. One handles the forward motion and the other half handles reverse motion. You have a controller with one side that has gone bad and the whole thing needs replaced. Sorry, but this can not be cheaply fixed and you need a new one. This is a great time to upgrade the controller to a better one.
You can by better quality after market EZGO PDS controllers for about the same price as replacing the stock one. The cheapest place to buy a replacement PDS controller is here.