Manifold Pressure/Vacuum Sensor: Description and Operation

MAP Sensor Location:

LOCATION

Sensor is mounted on throttle body and connected to manifold vacuum.

PURPOSE

Engine controller uses this input to adjust air/fuel mixture.

OPERATION

Engine controller supplies 5 volt sensor reference voltage. Sensor 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).

TYPICAL READINGS

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.