If you want to rework your own harness, you need to ensure that you properly crimp your terminals for positive connection that will not degrade or come loose over time. These are the most inexpensive set of crimping pliers that are used throughout the harness, yet still, maintain good quality. I am still working with my first set, and they have not loosened or become damaged.
 
Don't risk using an inferior crimp tool and end up chasing electrical gremlins. Use the tool the Pro's use for assembly, and make sure your rework lasts you for years down the road - literally!