Its is imperative now-a-days that the furnace you install has a COMPLETE and DEDICATED ground. There are 2 main reasons for this, 1) The PCB (control board) needs a good ground in order to operate properly (especially for communicating and ECM equipment). 2) Ground is needed in order for the flame rectification process to work.  

                   Here are a couple of ways to verify that you have a proper ground:

First, do a COMPLETE visual inspection of the circuit. Make sure the ground wire is dedicated (not shared with anything), and make sure it makes its way back to the electrical service panel of the home. Inspect junction boxes if needed, be thorough and do not assume anything!  Also make sure ALL grounding points are clean and tight.  

Set your meter to volts A/C take a voltage measurement between the neutral wire and "C" on the control board, you should see 2-volts or less.

Testing with ohms: set your meter to the ohm scale (100 or less) take a measurement between neutral and the burner/burner box or burner ground wire. This reading should be 10ohms or less.

Side note: Please do not use a meter or tool that will only display "GOOD", we need real numbers now-a-days. :) 

Carlos Sanchez