P0100

Circuit Description
The Mass Air Flow (MAF) sensor has a switched battery feed, a ground, and a signal circuit.

The MAF sensor used on this vehicle is a hot film type and is used to measure the air flow rate. The MAF output voltage is a function of the current required to keep the air flow sensing element at a fixed temperature. The air flowing through the sensor cools the sensing element. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, more current is required in order to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current to a voltage signal read by the ECM. The ECM calculates the air flow based on this signal.

The ECM monitors the MAF sensor signal voltage and can determine if the sensor signal voltage is too low, too high, not indicating the expected airflow for a given operating condition, or that the signal appears to be stuck based on the lack of normal signal fluctuations expected during engine operation.

Conditions for Running the DTC
^ The battery voltage is more than 11 volts.
^ One or both of the following DTCs not set: P1220, or P1120.
^ The engine speed is more than 500 RPM.

Conditions for Setting the DTC
The MAF signal indicates an airflow outside of a calculated range for a given RPM for at least 0.1 second.

Action Taken When the DTC Sets
^ The ECM illuminates the Malfunction Indicator Lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
^ The ECM will calculate the airflow from the other sensor inputs.

Conditions for Clearing the MIL/DTC
^ The ECM turns off the MIL after three consecutive drive trips that the diagnostic runs and passes.
^ A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
^ The ECM battery voltage is interrupted.
^ The scan tool clears the MIL/DTC.

Diagnostic Aids

Notice: Refer to J 35616-A Connector Test Adapter kit Notice in Service Precautions.

Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Check for the following conditions:
^ A plugged intake air duct or a dirty air filter element
^ Poor connections at the ECM or at the component-Inspect the harness connectors for any of the following conditions:
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- A poor terminal to wire connection
^ A damaged harness-Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. If the sensor signal is only affected when the harness is moved near a component, and there is no problem with the harness or connections, the component may be damaged.

Refer to Symptoms Preliminary Checks for the intermittents. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Monitoring the mass air flow sensor input will determine whether the fault is present now or intermittent.
6. Using the Freeze Frame data may aid in locating an intermittent condition. If the DTC cannot be duplicated, review the information in the Freeze Frame. Try to operate the vehicle within the same Freeze Frame conditions (the RPM, the MAF, the vehicle speed, the temperature etc.) that were noted. This process may help to recreate the malfunction.
9. Do not use B+ as a power source for this test, as this can damage the ECM.
12. The scan tool display should go to the maximum value for this parameter (about 72 grams per second).
24. The MAF sensor and the IAT sensor are to be replaced as an assembly. They are not serviced separately.
26. Perform the Idle Learn Procedure when replacing the ECM or throttle body.