Circuit Description

Mass Airflow (MAF) sensor measures amount of air entering engine during a given time. PCM uses MAF sensor information for fuel delivery calculations. MAF sensor readings during acceleration are much higher than those during deceleration or idle.

PCM calculates what MAF sensor reading should be received from sensor under certain conditions using engine speed (RPM), throttle position, and barometric pressure parameters. When these test conditions are met, PCM will compare its calculated MAF value to actual value received from sensor. If difference is too great, DTC will set.

Conditions required to set DTC are:

• Engine running.
• System voltage 9-16 volts.
• Throttle steady and TP ANGLE less than 50 percent.
• EGR DUTY CYCLE less than 50 percent.
• EGR PINTLE POS less than 50 percent.
• MAF signal frequency significantly higher or lower than predetermined value based on barometric pressure, throttle position and engine RPM
• Conditions present for greater than 12 seconds.