P0101

DTC P0101 Mass Air Flow (MAF) Sensor Performance






Circuit Description

The mass air flow (MAF) sensor is an air flow meter. The control module supplies the MAF sensor a signal circuit. An ignition positive voltage circuit and a ground circuit are supplied to the MAF sensor by independent circuits. The MAF sensor heats a wire element, or grid, within the MAF sensor in order to maintain 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 the 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 at wide open throttle-road load, the MAF sensor increases the frequency signal. The control module monitors the MAF sensor signal frequency in order 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 9 percent.
- The above conditions exist 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) the first time the diagnostic runs and fails.
- 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/Failure Records.

Conditions for Clearing the MIL or 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. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
- Use a scan tool in order to clear the DTCs.

Diagnostic Aids

Check for the following conditions:

- A skewed or stuck TP sensor. A problem with the TP sensor or TP sensor circuit can cause the VCM to incorrectly calculate the predicted mass air flow value. Observe the throttle angle with the throttle closed. If the throttle angle reading is not 0%, check for the following conditions:
- The throttle plate is sticking or excessive deposits on the throttle plate or the throttle bore.
- The TP sensor signal circuit shorted to voltage.
- A poor connection or high resistance in the TP sensor ground circuit.
- If none of the above conditions are noted and the throttle angle reading at closed throttle is not 0 percent, replace the TP sensor.
- 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.
- Rubber through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint.

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.