Possible causes

– Faulty Manifold Absolute Pressure sensor
– Manifold Absolute Pressure harness is open or shorted
– Manifold Absolute Pressure sensor circuit poor electrical connection
– Faulty Engine Control Module (ECM)

When is the code detected?

The sensor signal to the ECM is failing intermittently.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Engine rough idle
– Engine hesitation

P0109 MAZDA Description

The Manifold Absolute Pressure (MAP) sensor provides instantaneous manifold pressure information to the engine’s Engine Control Module (ECM). The data is used to calculate air density and determine the engine’s air mass flow rate, which in turn determines the required fuel metering for optimum combustion. A fuel-injected engine may alternately use a Mass Air Flow (MAF) sensor to detect the intake airflow.