when to replace timing chain and causes

If the check engine light is on, then the engiine control computer has detected a problem with the engine management system and has stored trouble codes. You need to get someone with a code scanner to check the system and tell you what's going on. As for timing chain, it should be good for almost the life of the car. Your problem is probably not the timing chain. I'm including a firectory link: http://repairpal.com/nissan-repair-in-pawtucket-rhode-island