P0102

Circuit Description
The Mass Air Flow (MAF) sensor measures the amount of air ingested by the engine. The direct measurement of the air entering the engine is more accurate than calculating the airflow from the MAP, the IAT and the engine speed (speed/density). The MAF sensor has a battery feed, ground, and a signal circuit. The MAF sensor used on this engine is a hot wire type. This engine uses the MAF sensor to measure air flow rate. The MAF output frequency is a function of the power required to keep the air flow sensing elements (hot wires) at a fixed temperature above the ambient temperature. Air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of air flow. The MAF sensor requires a greater amount of current in order to maintain the hot wires at a constant temperature as the air flow increases. The MAF sensor converts the changes in current draw to a frequency signal read by the PCM. The PCM calculates the air flow (grams per second) based on this signal.

The PCM monitors the MAF sensor frequency. The PCM can determine if the sensor is stuck low, stuck high, not providing the airflow value expected for a given operating condition, or that the signal appears to be stuck based on a lack of signal variation expected during the normal operation. This diagnostic monitors for too low of an airflow rate. When the PCM detects that the MAF sensor frequency is below a predetermined value, this DTC sets.

Conditions for Running the DTC
^ The engine is operating greater than 0.5 second.
^ The engine is at least 300 RPM.
^ The ignition voltage is at least 8.0 volts.
^ All conditions stable for 2.0 seconds.

Conditions for Setting the DTC
^ The Mass Air Flow frequency is less than 10 Hz.
^ All conditions met for greater than 1.0 second.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp on the second consecutive Ignition Cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive Ignition Cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure records.
^ The PCM utilizes speed density (RPM, MAP, IAT) for fuel management.

Conditions for Clearing the MIL/DTC
^ The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed (current DTC) clears when the diagnostic runs and does not fail.
^ A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
^ Use a scan tool in order to clear the MIL/DTC.

Diagnostic Aids

Important:
^ Remove any debris from the PCM/TAC module connector surfaces before servicing the PCM/TAC module. Inspect the PCM/TAC module connector gaskets when diagnosing/replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM/TAC modules.
^ For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter kit J 35616-A. Using this kit prevents damage to the harness/component terminals.
^ The following may cause an intermittent:
- Poor Connections.
- Mis-routed harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.
^ Any un-metered air may cause this DTC to set. Inspect for the following:
- An engine vacuum leak.
- The PCV system for vacuum leaks.
- An incorrect PCV valve.
- The engine oil dip stick not fully seated.
- The engine oil fill cap loose or missing.
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests whether the MAF sensor ignition feed circuit is shorted to a ground. If the fuse is open, repair the circuit as necessary and replace the fuse.
3. Monitoring the MAF sensor frequency will determine if the fault is present or the malfunction is intermittent.
4. Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
5. This step tests whether the 5.0 volts is available to the MAF sensor signal circuit.
6. This step tests if the signal circuit is shorted to another 5.0 volt reference circuit. If another DTC sets, repair the circuits that are shorted together. If no DTCs set it may be necessary to road test the vehicle.
11. Inspect the fuse 19 for being open. If the fuse is open, inspect the MAF sensor ignition feed circuit for a short to ground.
12. This step verifies whether B+ is available to the MAF sensor.