Circuit Description

Mass Airflow (MAF) sensor is hot-wire type and is used to measure airflow rate into engine. MAF sensor has a battery feed, ground and signal circuit. As airflow increases, a greater amount of current is required to maintain hot wires at a constant temperature. MAF sensor converts changes in current draw to a frequency signal read by PCM. PCM calculates airflow (grams per second) based on this signal.

PCM monitors MAF sensor frequency and can determine if sensor is stuck low, stuck high, not providing airflow value expected for a given operating condition, or that signal variation expected during normal operation is not present.

This test checks for a stuck MAF sensor signal. If MAF sensor frequency varies less than a predetermined minimum amount, DTC will set.

DTC will set when following conditions are present:

• Engine running.
• Engine speed at greater than 300 RPM.
• Ignition voltage at least 8 volts.
• MAF frequency less than 10 Hz.
• Conditions met for one second.