You should not start validation unless you expect to pass. The most expedient way to accomplish this is by giving your parts a chance to fail on accelerated test exposures that are similar to those that your product will see in validation and in the field.
A sound validation plan protects the customer and your company from field failures by exposing the Right Parts to the Right Tests. This article summarizes the steps used to develop this plan.
An example of an automotive validation test reliability target is R97C50. Does this mean that a field failure rate of 3% can be expected?