Dynasty L4-153 2.5L SOHC VIN K TBI (1992)
Manifold Pressure/Vacuum Sensor: Description and Operation
Location
Sensor mounted passenger side firewall.
Purpose
At start-up, the Control Module uses sensor to read barometric (atmospheric), pressure, for reference, to calculate air/fuel mixture.
During operation the Control Module monitors sensor input to adjust spark advance and air/fuel mixture.
Operation
PCM supplies 5 volt sensor reference voltage.
Sensor, connected to manifold vacuum at throttle body, converts intake manifold pressure into voltage.
Theory
Sensor resistance and manifold absolute pressure are inversely proportional (as manifold absolute pressure increases, (low vacuum), sensor
resistance decreases and vice versa).
Output Voltages
Sensor output voltage range is 0.5 to 4.5 volts.
^ Output voltages between 0.5 and 1.5 volts indicate a high vacuum situation, such as idle or deceleration.
^ Output voltages between 1.5 and 3.0 volts indicate a medium level of vacuum such as a cruise or slight acceleration condition.
^ Output voltages between 3.0 and 4.5 volts indicate a low vacuum situation such as hard acceleration or a mechanical failure.
^ Any reading of 0 volts or over 5 volts indicates a problem.
