P0101

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Mass Air Flow (MAF) sensor measures the amount of air which passes through it into the engine. The Powertrain Control Module (PCM) uses the mass air flow information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle.

The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency will vary within a range of around 2000 Hertz at idle to near 9000 Hertz at maximum engine load. DTC P0101 will be set if the signal from the MAF sensor does not match a predicted value based on barometric pressure, air density, manifold pressure, throttle position, and engine RPM.

CONDITIONS FOR RUNNING THE DTC
^ The engine is running.
^ Ignition voltage is between 9.0-18.0 volts.
^ Throttle angle is less than 25 percent.
^ MAP and TP steady for more than 5 seconds.

CONDITIONS FOR SETTING THE DTC
The difference between actual airflow and predicted airflow is more than the calibrated value.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
^ If the misfire is determined to be catalyst damaging, the PCM will flash the MIL.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following conditions:
^ A restricted intake air duct or dirty air filter element
^ A loose or misrouted air duct.
^ The actual Mass Air Flow is compared to a calculated Mass Air Flow based on the MAP, TP, and engine RPM readings. A skewed unresponsive MAP sensor at key ON will cause the calculated Mass Air Flow value to be inaccurate. When the engine is started a calculated difference between actual Mass Air Flow and Calculated Mass Air Flow occurs. DTC P0101 will set, the vehicle will stall, a default Mass Air Flow based on the MAP sensor will occur. Because the MAP sensor is skewed/unresponsive the default Mass Air Flow values are incorrect and the vehicle may not restart. If a fault occurs which causes the MAP sensor value to be incorrect, such as, poor vacuum connections, damaged vacuum source, defective vacuum hoses, or unmetered air into the manifold, DTC P0101 will set and the default Mass Air Flow value will be substituted. Because the MAP sensor value is incorrect the vehicle may not start and run.
^ Skewed or stuck TP sensor- A faulty TP sensor or TP sensor circuit can cause the PCM to incorrectly calculate the predicted Mass Air Flow value. Observe Throttle Angle with the throttle closed. If the Throttle Angle reading is not 0 percent, test for a TP sensor signal circuit shorted to voltage:
^ If none of the above conditions are noted and the Throttle Angle reading at closed throttle is not 0 percent, replace the TP sensor.
^ Skewed MAP sensor- A skewed MAP sensor can cause the BARO reading to be incorrectly calculated. To check the MAP sensor, compare the MAP/BARO reading on the vehicle being diagnosed to the MAP/BARO reading on a normally operating vehicle. If a large difference is noted replace the MAP sensor.
^ Misrouted harness- Inspect the MAF sensor harness to ensure that it is not routed too close to high voltage wires such as spark plug leads.

IMPORTANT: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection.
Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Diagrams.
^ Damaged harness.
Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Circuit Testing and Wiring Repairs in Diagrams.
^ Inspect the PCM and the engine grounds for clean and secure connections.

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table:
3. Only if sent here from the Engine Cranks But Does Not Run, continue to follow diagnostic table even if DTC P0101 has NOT failed this ignition.
4. This step tests the MAP sensor. By disconnecting the MAF sensor, the vehicle is forced into speed density. Speed density is based on the MAP, TP, and engine RPM readings. With a skewed/unresponsive MAP sensor, the speed density calculation is incorrect and the vehicle may not start. For further information refer to Diagnostic Aids.
5. This step tests for a skewed or sticking MAP sensor. The MAP sensor should respond smoothly and gradually as RPM is increased. Compare the MAP sensor of the affected vehicle to that of a normally operating vehicle, if a large difference is noted replace the MAP sensor.
9. This step verifies that the ignition feed voltage and a good ground are available at the MAF sensor.