P0101

Circuit Description
The Mass Air Flow (MAF) sensor is an air flow meter. The Control Module (PCM/VCM) supplies the MAF sensor a signal circuit. An ignition voltage is supplied to the MAF sensor by an independent circuit. A ground is supplied to the MAF sensor by an independent circuit. The MAF sensor heats a wire element, or grid, within the MAF sensor in order to a calculated temperature. As inlet air flows across and cools the grid, the MAF sensor increases current flow to the grid in order to maintain a constant grid temperature. The MAF sensor converts the grid current flow into a frequency signal. The Control Module converts the MAF signal frequency into a grams per second value. During low air flow rates, such as at engine idle, the MAF sensor produces a low frequency signal. During high air flow rates, such as Wide Open Throttle-road load, the MAF sensor increases the frequency signal. The Control Module monitors the MAF sensor signal frequency to calculate the flow and mass of the air entering the engine.

The VCM monitors the MAF sensor air flow rate and compares this signal to a VCM calculated air flow rate. The calculated air flow is based on engine speed and barometric pressure. The VCM uses the MAP sensor in order to determine the barometric pressure when the ignition key is turned ON but before the engine is cranking or running. This DTC will be set if the MAF sensor signal airflow rate does not match the air flow rate calculated by the VCM.

Conditions for Running the DTC
^ The engine is running
^ No active TP sensor DTCs
^ No active MAP sensor DTCs
^ No active EVAP DTCs
^ No active CKP sensor DTCs
^ No active IAT sensor DTCs
^ DTC P0401 not active
^ DTCs P0102 and P0103 not active
^ The system voltage is between 11-16 volts
^ The EVAP canister purge duty cycle is 99.6 percent or less
^ The TP sensor voltage is steady
^ The EGR duty cycle is less than 90 percent
^ The EGR pintle position is less than 90 percent
^ The throttle position is less than 90 percent
^ The above conditions present for more than 2 seconds

Conditions for Setting the DTC
^ The actual MAF value is not equal to the calculated MAF value
^ The above condition exists for more than 5 seconds

Action Taken When the DTC Sets
^ The Control Module illuminates the Malfunction Indicator Lamp (MIL) if a failure is detected during 2 consecutive key cycles.
^ The Control Module will set the DTC and records the operating conditions at the time the diagnostic fails. The Control Module stores the failure information in the scan tools Freeze Frame and/or the Failure Records.

Conditions for Clearing the MIL/DTC
^ The Control Module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the Engine Coolant Temperature is more than 70°C (158°F) during the same ignition cycle).
^ Use the scan tool Clear Information function.

Diagnostic Aids
Check for the following conditions:
^ A misrouted harness. Inspect the MAF sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads.
^ A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the connectors and the wiring harnesses related to the MAF sensor. A change in the display indicates the location of the fault.
^ A plugged intake air duct or dirty air filter element. A Wide Open Throttle acceleration from a stop should cause the mass air flow displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or more at the time of the 1-2 shift. If not, check for a restriction.

An intermittent may be caused by any of the following conditions:
^ A poor connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Correct any MAP sensor DTCs first. The value shown for the MAP sensor varies with altitude. The value decreases by approximately 3.0 kPa for every 1000 feet of altitude. 105 kPa is the approximate value displayed at or near sea level.
8. This step verifies that the problem is present at idle.
10. A voltage reading of less than 4.0 volts or over 6.0 volts at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection.
11. This step verifies that the ignition positive voltage circuit and a good ground are available at the MAF sensor.