Circuit Description

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

VCM calculates what MAF sensor reading should be received from sensor under certain conditions using engine speed (RPM), throttle position, and altitude parameters. When these test conditions are met, VCM will compare its calculated MAF value to actual value received from sensor.

Conditions required to test for DTC are:

• Engine running.
• No EVAP, MAP or TP sensor DTCs set.
• EGR DTC P0401 not set.
• MAF sensor DTC P0102 or P0103 not set.
• System voltage 11-16 volts.
• Canister purge duty cycle 99.6 percent or less.
• Change in throttle position 3.9 percent or less.
• EGR duty cycle not greater than 89.8 percent.
• EGR pintle position not greater than 89.8 percent.
• Engine vacuum 75 kPa or less.
• TP not greater than 89.8 percent.
• Conditions met for greater than 2 seconds.