Method of measuring barometric pressure and manifold absolute pressure using a single sensor

Claim 1

In an electronic control system for an engine, the system having sensors to monitor various engine and vehicle parameters, including manifold absolute pressure (MAP), vehicle speed and ambient temperature, the system also having memory means for storing data values representing the various engine and vehicle parameters, as well as for storing a predetermined control strategy, the system further having a solenoid to vent the MAP sensor to atmosphere, the system further having computer means for utilizing the data values along with the control strategy to control the engine, a barometric pressure read technique for utilizing the MAP sensor to measure barometric pressure dynamically while the engine is operating and for controlling the engine while the MAP sensor is dedicated to measuring the barometric pressure, comprising: branching to the barometric pressure read technique from the control strategy; determining whether the throttle is in a predetermined position; returning to the engine control strategy if the throttle is at a position other than the predetermined position; determining whether the system is due for a barometric pressure update, returning to the engine control strategy if it is not; determining whether the actual engine RPM is greater than the maximum allowable RPM set for a barometric pressure update, returning to the engine control strategy if it is; energizing a solenoid to vent the MAP sensor to atmosphere, holding the last MAP sensor reading for use in the engine control strategy during the following barometric read time period; determining if the solenoid "on" time is less than the predetermined barometric pressure stabilization time, delaying until the solenoid "on" time is equal to or greater than the barometric pressure stabilization time; utilizing the MAP sensor to read barometric pressure; de-energizing the solenoid; determining whether the solenoid "off" time is less than the MAP sensor's stabilization time, delaying, if needed, until the solenoid "off" time is equal to or greater than the MAP sensor stabilization time; resuming the engine control strategy using the MAP sensor for MAP readings and the new barometric pressure reading.