P0100
CIRCUIT DESCRIPTION
The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by the engine. The direct measurement of air entering the engine is more accurate than calculating the airflow from the other sensor inputs. The MAF sensor has a switched battery feed, a ground, a signal circuit and a signal return 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 power required to keep the air flow sensing any elements at a fixed temperature above ambient temperature. The air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of the air flow. As the air flow increases, a greater amount of current is required in order to maintain the hot film at a constant temperature. The MAF sensor converts the changes in current draw 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 engine speed is greater than 400 RPM.
OR
While cranking, the engine speed is greater than 120 RPM.
CONDITIONS FOR SETTING THE DTC
The MAF signal indicates an airflow of less than 4 kg/h (1.38 g/s) or exceeds the maximum value for a given RPM as specified in the table
in the accompanying image:
The above conditions are present 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 does not fail.
^ A History DTC clears after forty consecutive warm-up cycles if no failures report by this diagnostic or any other emission related diagnostic.
^ The ECM battery voltage is interrupted. The scan tool clears the MIL/DTC.
DIAGNOSTIC AIDS
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:
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
Refer to Overall Vehicle Information / Diagrams / Diagnostic Aids Checking Terminal Contact procedure.
^ A misrouted harness. Inspect the harness in order to ensure that the harness is not routed too close to the high voltage wires such as the spark plug leads, or too close to the high current devices such as the alternator, the motors, the solenoids etc.
^ 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.
^ A plugged intake air duct or a dirty air filter element.
Refer to Symptoms / Intermittents. Testing and Inspection
TEST DESCRIPTION
The number(s) below refer to the step numbers on the diagnostic table.
2. Monitoring the MAF sensor signal voltage 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.
12. The scan tool display should go to the maximum value for this parameter (about 5 volts), although the actual voltage through the test light is higher.