Q: Heater is running cold, engine light is on, rough idle

Hello there, many faults will cause your heat to blow cold and check engine light on with your 2007 Honda CRV. The first step in diagnosis would be to check what code your car has stored in the computer, this code will indicate in which vehicle system the fault lies and can help pinpoint what is going on. With heating issues there are interior heating issues that can cause the heat to blow cold, or a cooling system fault can cause the heating system to blow cold. Interior faults that can cause this issue are the blend mode door, AC control module, or a failing heater core. Cooling system faults such as air in the system, coolant leaks, or faulty thermostat will also cause the heater to blow cold. If the vehicle shows signs that is it getting close to overheating it should be shut off and not driven, overheating the engine can damage it. A qualified Technician such as one from YourMechanic will be able to diagnose your check engine light and the heating system.