Manifold Absolute Pressure (Map) Sensor - Mercury 150 EFI Service Manual

IGNITION

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is located on top of the air plenum. The ECM regulates fuel flow, in part,
based on manifold absolute pressure. The MAP sensor becomes more critical in engine
running quality as the engine is operated at higher altitudes (i.e. mountain lakes). Should
the MAP sensor fail, the ECM will default to a value of approximately 14.7 psi.
The Digital Diagnostic Terminal (DDT) can be used to determined whether the MAP sen-
sor is functioning properly. As throttle is advanced, numerical value on DDT display
should increase. As throttle is retarded, numerical value should decrease indicating MAP
sensor is functioning. If numerical value does not change as throttle setting varies, MAP
sensor is defective.
NOTE: If MAP sensor is not functioning, #4 LED indicator light on DDT will be illuminated.
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Manifold Absolute Pressure (MAP) Sensor
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90-883728 JULY 2001
58898