Signal Function

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The MAF sensor measures the airflow rate into the engine and provides an analog signal to the powertrain control module (PCM) which is used to calculate air flow for the exhaust gas recirculation (EGR) monitor.

The current PCM implementation contains a mass airflow interface, which consists of a 2-pole, differential input, low pass filter. This filter is designed to pass an analog signal, originating from the mass air sensor, while rejecting unwanted ignition noise, high frequency electrical interference, and ground offsets.

The input to the interface is the analog voltage signal difference between MAF+ (mass airflow signal) and MAF- (mass airflow return). The MAF sensor outputs an analog voltage signal calibrated to 0.5 V at the lower limit of the flow range and 4.75 V at the upper limit of the flow range.

The intake air temperature (IAT) is also integrated into the MAF sensor.

CAUTION: The PCM harness connectors must be properly seated and the connector latch properly attached to eliminate possible driveability concerns or a no start condition. Installing the PCM connectors on an angle may cause an improper connection, misdiagnosis, and damaged components. Install the connector until the lever pivots and seats itself. Apply light pressure to get the connector into position on the PCM and then fully seat the connector.

NOTE: Visually inspect the harness connectors for corrosion, damage, proper mating, and correct pin tension.

This pinpoint test is intended to diagnose the following:

MAF sensor
harness circuits: MAF SIG, MAF RTN, vehicle power (VPWR), and power ground (PWR GND)
PCM

Fig 1: Identifying PCM Body Harness Connector And MAF/IAT Sensor Connector

Courtesy of FORD MOTOR CO.