* The cracked manifold pan likely caused the issue: A cracked intake manifold (or, as you called it, a "manifold pan") is a serious problem. It can cause:
* Vacuum leaks: A crack allows air to enter the intake system at the wrong point, disrupting the carefully measured air-fuel mixture. This will almost certainly trigger a check engine light, as the engine's computer detects a problem with its operation.
* Exhaust leaks: Depending on the location of the crack, it might allow exhaust gases to leak into the intake, seriously harming the engine's performance and potentially leading to catastrophic damage. This would also cause a check engine light.
* Misfires: The incorrect air/fuel mixture due to the leak can cause misfires, resulting in the check engine light illuminating.
* The dealer might have missed something: While they informed you of the crack, they may not have fully addressed it. Perhaps they only reported the problem without repairing it, hoping you'd authorize the repair later. Or, even worse, the repair they attempted was inadequate.
* Secondary effects: The crack could have caused other related problems, even if seemingly unrelated. For example, a vacuum leak might put stress on other components, leading to further issues and more trouble codes.
In short: The most likely scenario is that the cracked manifold pan is the direct cause of the check engine light. You should return to the Nissan dealer immediately and demand they address the issue. Explain that the check engine light appeared shortly after they informed you of the crack, strongly suggesting a direct link. This is crucial because you may have a warranty or some form of recourse based on their initial diagnosis. Don't delay; driving with a cracked manifold and a check engine light can cause serious engine damage.
