P0101

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Mass Air Flow (MAF) sensor measures the amount of air entering the engine during a given time. The VCM uses the mass air flow information for the fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation. A small quantity of air indicates a deceleration or an idle situation.

The MAF sensor produces a frequency signal which can be monitored by using a scan tool. The frequency varies within a range of around 5 to 7 g/s at idle to approximately 125 g/s at the maximum engine load.

CONDITIONS FOR SETTING THE DTC

The following conditions will set the OTC:

^ The engine is running

^ No TP sensor DTCs

^ No MAP sensor DTCs

^ No EVAP DTCs

^ The EGR DTC P0401 is not active

^ The MAF DTCs high/low are not active

^ The crank sensor DTCs are not active

^ The system Voltage is between 11-16 volts

^ The Canister Purge Duty Cycle is less than or equal to 99.6%

^ The change in throttle position is less than or equal to 3.9%

^ The EGR duty cycle is no more than 89.8%

^ The EGR Pintle Position is no more than 89.8%

^ The engine vacuum is less than or equal to 75 kPa

^ The throttle position is no more than 89.8%

^ The above conditions met for greater than 2 seconds

ACTION TAKEN WHEN THE DTC SETS

^ The VCM illuminates the Malfunction Indicator Lamp (MIL) the first time the fault is detected.

^ The VCM calculates an airflow value based on the idle air control (IAC) valve position, the throttle position, the engine speed, and the barometric pressure.

^ The VCM will store the conditions which were present when the DTC set as Freeze Frame and the Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

Check for the following conditions:

^ A skewed or stuck TP sensor. A malfunctioning TP sensor or TP sensor circuit can cause the VCM to incorrectly calculate the predicted mass air flow value, Observe the Throttle Angle with the throttle closed. If the Throttle Angle reading is not 0%, check for the following conditions:

- The throttle plate sticking or excessive deposits on the throttle plate or the throttle bore

- The TP sensor signal circuit Is shorted to voltage

- A Poor connection or high resistance in the TP sensor ground circuit.

If none of the above conditions are noted and the Throttle Angle reading at closed throttle is not 0%, replace the TP sensor.

^ Inspect harness connectors for the following conditions:

- Backed out terminals

- Improper mating

- Broken locks

- Improperly formed or damaged terminals

- Poor terminal to wire connection

^ A misrouted harness. Inspect the MAF sensor harness in order to ensure that it is not routed too close to high voltage wires such as spark plug leads.

^ A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the connectors and the wiring harnesses related to the MAF sensor. A change in the display indicates the location of the fault.

^ A plugged intake air duct or a dirty air filter element. A wide open throttle acceleration from a stop should cause the Mass Air Flow displayed on a scan tool to increase from about 4-7 gm/s at idle to 100 gm/s or greater at the time of the 1-2 shift. If not, check for a restriction.

^ A skewed MAP sensor. A skewed MAP sensor can cause the BARO reading to be incorrectly calculated. In order to check the MAP sensor, compare the BARO reading on the vehicle being diagnosed to the BARO reading on a normally operating vehicle. If a large difference is noted (over 8 kPa), replace the MAP sensor. Refer to MAP Sensor Replacement.

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.

2. The MAP system performance or rationality diagnostic uses the MAP sensor signal along with other inputs in order to calculate an expected airflow rate. The VCM then compares the expected flow rate to the actual measured airflow from the MAF sensor. The first few steps of this table verify that the MAP sensor is working properly. Correct any MAP sensor DTCs first. The value shown for the MAP sensor varies with altitude. The value decreases by approximately 3.0 kPa for every 1000 feet of altitude. 100 kPa is the approximate value displayed at or near sea level.

6. This step verifies that the problem is present at idle.

10. A voltage reading of less than 4.0 volts or over 6.0 volts at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection.

11. This step verifies that the ignition feed circuit voltage and a good ground are available at the MAF sensor.