A system and method for monitoring tire pressure in a tire of a vehicle is described, in which a tire pressure reading in the tire and an ambient pressure reading are received, and a warning indicator visible to an operator of a vehicle is selectively activated based on the tire pressure reading, the ambient pressure reading, and a predetermined threshold. In one embodiment, the ambient pressure is used by an engine control system for regulating the air-fuel intake, transmitted to a communications bus, and used by a tire pressure monitoring subsystem configured for receiving the ambient pressure reading from the communications bus.