if you are getting the coil pack replaced from the same dealer you bought the car from, then the replacement is covered under the warranty till the time of your car warranty. Few weeks back, the dealer of my car replaced the cols for free, which means it is under warranty. But please remember, if you are getting it replaced from another dealer, it does not conclude in the warranty. Rather the warranty will automatically become void if you get any part replaced from any other workshop or dealer.