P0101

DTC P0101 Mass Air Flow System Performance




Circuit Description
The Mass Air Flow (MAF) sensor is a hot wire type air flow meter. The MAF sensor uses ignition voltage, a ground and a signal circuit. The signal circuit is the input to the VCM. The MAF heats a wire element in the air flow stream to a predetermined temperature. As inlet air flows across and cools the wire element, the MAF sensor increases current flow to the wire element in order to maintain a constant element temperature. The MAF sensor converts this current flow into a frequency signal. The VCM monitors the MAF signal frequency and determines the flow and mass of the air entering the engine.

The VCM converts the MAF signal frequency into a grams per second value. During low air flow rates (such as at engine idle) the MAF sensor will produce a low frequency signal (approximately 2000 Hz or 6 grams/second). During high air flow rates such as wide open throttle at road load, the MAF sensor will produce a high frequency signal (approximately 9000 HZ or 125 grams/second).

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 DTC
- 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 Canister Purge Duty Cycle is less than 99%
- The TP sensor voltage is steady
- The EGR duty cycle is less than 90%
- The EGR Pintle Position is less than 90%
- The throttle position is less than 90%
- The above conditions met for greater than 2 seconds

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

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

Conditions for Clearing the MIL/DTC
- The VCM 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 startup 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 a 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.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 2:

Steps 3 - 4:

Steps 5 - 7:

Steps 8 - 12:

Steps 13 - 18:

Steps 19 - 22:

Steps 23 - 24:

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. The MAP system performance or rationality diagnostic uses the MAP sensor signal along with other inputs in order to calculate an expected airflow rate. The VCM then compares the expected flow rate to the actual measured airflow from the MAF sensor. The first few steps of this table verify that the MAP sensor is working properly. 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. 100 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 feed circuit voltage and a good ground are available at the MAF sensor.