Amigo 4WD L4-2.3L (4ZD1) (1989)
MAP Sensor Vacuum Switching Valve: Description and Operation
MAP Sensor Vacuum Switching Valve
To alternate MAP sensor readings between intake manifold pressure and atmospheric pressure, the system utilizes an ECM-controlled vacuum switching
valve (VSV). To switch the input signal to atmospheric pressure, the ECM energizes the VSV for about one second under these conditions:
1.
When the ECM is reset.
2.
When these three conditions exist simultaneously:
a. Engine speed is less than 200 rpm.
b. Battery voltage is more than 9.5V.
c. Vehicle speed is less than 1 km/h.
3.
When the ECM judges a high altitude condition, it takes an atmospheric pressure reading and sets its "barometric map." High altitude is indicated
when the MAP sensor signal indicates less than 596 mmHg absolute pressure.