The 2005 Honda Civic EX with the 1.7L engine has a timing belt, not a chain. The timing belt for this application will cost about $20-30, depending on brand. The manufacturer's suggested replacement interval is at 110,000 miles or 84 months. If the car is regularly driven in extreme temperatures, the belt should be replaced at 60,000 miles. In any case, it's a good idea to at least inspect the belt and related components (water pump, tensioner) at around 60K miles.