Will the check engine light come on when water pump is bad 2004 grand prix?

Not directly. A bad water pump itself won't usually trigger the check engine light on a 2004 Pontiac Grand Prix. The check engine light illuminates when the car's computer detects a problem with a monitored system. A failing water pump doesn't usually trigger those sensors.

However, a failing water pump can *cause* other problems that *will* trigger the check engine light. For example:

* Overheating: If the water pump fails completely, the engine will overheat. The car's computer will detect this high temperature and illuminate the check engine light, likely along with the temperature warning light. This is the most likely scenario.

* Low coolant level: A leaking water pump can cause a loss of coolant. The computer may detect low coolant level (depending on the car's sensors), though this isn't always the case.

In short: A bad water pump won't directly cause the check engine light. However, the consequences of a bad water pump—severe overheating—almost certainly will. If your Grand Prix is overheating, get it checked immediately to prevent serious engine damage.