P0101

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Mass Air Flow (MAF) sensor measures the amount of air that is ingested by the engine. Direct measurement of air entering the engine is more accurate than calculating airflow from MAP, IAT and RPM (speed/density). The MAF sensor has a battery feed, ground and signal circuit.

The MAF sensor used on this vehicle is a hot wire type and is used 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 ambient temperature. Air flowing through the sensor cools the sensing elements. The amount of cooling is proportional to the amount of air flow. As air flow increases, a greater amount of current is required to maintain the hot wires at a constant temperature. The MAF sensor converts the changes in current draw to a frequency signal read by the PCM. The PCM calculates air flow (grams per second) based on this signal.

The PCM monitors the MAF sensor frequency and 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 normal operation. This diagnostic checks the range/performance of the MAF sensor. The MAF system performance or rationality diagnostic uses MAP, IAT and RPM to calculate an expected airflow rate that is then compared to the actual measured airflow from the MAF sensor. The actual MAF value and the calculated value are only compared during conditions where they are likely to match. If the actual MAF reading is not within a predetermined range of the calculated reading, this DTC will set.

CONDITIONS FOR SETTING THE DTC

^ DTCs P0100, P0102, P0103, P0122, P0123, P0107, P0108 not set.

^ Engine running.

^ Engine speed greater than 50 RPM but less than 2800 RPM.

^ TP sensor angle less than 50% when engine vacuum (MAP) is greater than 40 kPa.

^ Ignition voltage greater than 10 volts.

^ Actual MAF reading does not match calculated MAF reading (speed density).

^ All above conditions stable for entire MAF test. All conditions met for 5 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.

^ The PCM will utilize speed density (RPM, MAP, IAT) for fuel management.

^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and/or Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

^ A last test failed (Current DTC) will clear when the diagnostic runs and does not tail.

^ A History DTC will clear after forty consecutive warm-up cycles, it no failures are reported by this or any other emission related diagnostic.

^ PCM battery voltage is interrupted.

^ Using a Scan tool.

DIAGNOSTIC AIDS

^ An intermittent may be caused by the following:

- Mis-routed harness.

- Rubbed through wire insulation.

- Broken wire inside the insulation. For intermittents, refer to Symptoms. Testing and Inspection

^ Any un-metered air may cause this DTC to set. Check 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.

TEST DESCRIPTION

Number(s) below refer to step numbers on the diagnostic table.

2. The MAF system performance or rationality diagnostic uses the MAP sensor signal along with other inputs to calculate an expected airflow rate that is then compared to the actual measured airflow from the MAF sensor. The first few steps of this table verity that the MAP sensor is working properly. Any MAP sensor DTC should be corrected first. The value shown for the MAP sensor will vary with altitude. The value will decrease by approximately 3 kPa for every 1000 feet of altitude. 100 kPa is the approximate value displayed at or near sea level.

6. Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC tailed. For any test that requires back probing the PCM or component harness connectors, must use the Connector Test Adapter Kit J 35616A. Using this kit will prevent any damage to the harness connector terminals.

7. Any un-metered air may cause this DTC to set. Check PCV system for vacuum leaks. Also inspect dip stick for being pulled out. Check oil fill cap for being loose.

8. Verifies the signal circuit from the MAF sensor electrical connector to the PCM.

9. Verifies whether a ground and B+ circuit is available.

10. Checks for a signal circuit for an open.

11. Checks for a signal circuit shorted to B+.