P0101

Schematic:

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 tests the range/performance of the MAF sensor. The MAF system performance or rationality diagnostic uses the MAP, the IAT, and the engine speed to calculate an expected airflow rate. The PCM then compares the rate to the actual measured airflow from the MAF sensor. The PCM only compares the actual MAF value and the calculated value during conditions where the values are likely to match. This DTC sets if the actual MAF reading is not within a predetermined range of the calculated reading.

CONDITIONS FOR RUNNING THE DTC
DTCs P0102, P0103, P0107, P0108, P0121, P0122, P0123 not set.
^ The engine is running.
^ The TP sensor angle is less than 50 percent and the engine vacuum (BARO-MAP) is greater than 65 kPa.
^ The system voltage is more than 11 volts but less than 18 volts.
^ The EGR pintle position is less than 90 percent.
^ The change in TP sensor is less than 3 percent.
^ All above conditions stable for 2.0 seconds.

CONDITIONS FOR SETTING THE DTC
^ The MAF frequency is 50 percent different from the speed density calculation.
^ All conditions met for 5.0 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) 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.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the Malfunction Indicator Lamp (MIL) OFF after 3 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 40 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 connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
^ For any test that requires probing the PCM or component harness connectors, use the J 35616-A connector test adapter kit. Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Diagrams for procedures.
^ 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
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION

Steps 1 - 6:

Steps 7 - 16:

Steps 17 - 22:

The numbers below refer to the step numbers on the diagnostic table.
2. The MAF system performance or rationality diagnostic uses the MAP sensor signal along with other inputs in order to calculate an expected airflow rate. The PCM then compares the expected flow rate to the actual measured airflow from the MAF sensor. The first few steps of this table verifies the MAP sensor is working properly. Correct any MAP sensor DTCs first.
3. The MAP sensor is difficult to remove. Twist the MAP sensor forward and pull up. This forward motion clears the retaining clip.
5. This step monitors a smooth transition to the original scan tool value.
6. 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.
7. Any un-metered air causes this DTC to set. Inspect the PCV system for vacuum leaks. Also inspect the dip stick for being pulled out. Inspect the oil fill cap for being loose.
8. This step verifies the signal circuit from the MAF sensor electrical connector to the PCM.
9. This step verifies whether a ground and B+ circuit is available.
10. This step tests the signal circuit for an open.
11. This step tests the signal circuit for a short to B+.