Circuit Description

This test determines if Mass Airflow (MAF) sensor is providing proper readings to PCM. MAF sensor is a high frequency device that measures rate of airflow through throttle body. MAF sensor outputs a series of pulses that varies in frequency with airflow. PCM uses this signal for fuel control.

MAF sensor readings during acceleration will be much higher than those during deceleration or idle. PCM calculates what MAF sensor reading should be from the sensor under certain conditions using engine speed (RPM), throttle position, and altitude parameters. When certain test conditions are met, PCM will compare its calculated MAF value to the actual value received from the sensor. The calculated MAF reading is calculated by comparing MAP, RPM and IAT values. If difference between calculated MAF and actual MAF is too great, DTC will set.

For duplication of DTC, ensure:

• No TP senor, MAP sensor or system voltage DTCs are set.
• System voltage is 11-18 volts.
• Canister purge duty cycle is less than or equals 90 percent.
• EGR pintle valve movement less than 90 percent.
• TP sensor angle is steady and less than 48 percent.