HOLDEN GEN III V8, Service Training

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GEN III V8 ENGINE MANAGEMENT
MANIFOLD ABSOLUTE PRESSURE SENSOR
The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which
result from engine load (intake manifold vacuum) and RPM changes and converts these into a voltage output.
The control module sends a 5-volt supply voltage to the MAP sensor. As the manifold pressure changes, the
output voltage of the sensor also changes. By monitoring the sensor output voltage, the control module knows
the manifold pressure.
A closed throttle during engine coast down would
produce a relatively low MAP output, while a wide
open throttle would produce a high output. This
high output is produced because the pressure
inside the manifold is the same as outside the
manifold during wide open throttle, so it measures
100% of outside air pressure (atmospheric
pressure). The MAP sensor is also used, to
measure barometric pressure, allowing the control
module to make adjustments for different operating
altitudes.
With the engine running, the MAP output voltage
signal should vary from about 1.0 to 1 . 5 volts at
idle, to about 4.0 to 4.5 volts at wide open throttle.
This MAP output voltage signal is sent to the
control module MAP sensor input signal terminal.
With ignition on and engine stopped, the manifold
pressure is equal to atmospheric (or barometric)
pressure and the signal voltage output will be high,
close to 5 volts at sea level. This voltage is used by
the PCM as an indication of engine load and
atmospheric pressure, altitude and is referred to as
BARO.
MAP Sensor Circuit
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