Vacuum Switch: Description and Operation

Secondary Port Throttle Valve System Control Circuit Diagram:

PURPOSE
A vacuum sensor is used to monitor vacuum at the secondary port throttle valve actuators. The signal from this sensor is used to determine if the secondary port throttle valve system is operating properly.


OPERATION
The computer sends a 5.0 volt reference voltage to the vacuum sensor, which divides the current from the reference source between the signal circuit and ground at different ratios, depending on vacuum. This varies the voltage in the signal circuit so that when there is no vacuum present at the sensor, the voltage output to the ECM is low. During "NORMAL" power mode operation, there should be no vacuum at the actuators and the voltage signal from the vacuum sensor should be 0.54 - 0.62 volts. During "FULL" power operation, vacuum is applied to the secondary port throttle valve actuators and the sensor signal should be 1.3 - 3.1 volts, indicating vacuum at the actuators. The ECM monitors the signal from the vacuum sensor and compares that information with the commanded status of the system. If the system is in "NORMAL" mode, and the vacuum sensor signal indicates vacuum is being applied to the actuators, a code 61 will set. If the system is in "FULL" power mode and there is no indication of vacuum at the actuators, a code 61 will also set.