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 PCM uses the mass air flow information to monitor EGR flow rates. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle.

The MAF sensor produces a frequency signal. DTC P0101 will be set if the signal from the MAF sensor does not match a predicted value based on, engine coolant temperature, throttle angle and engine speed.

Conditions for Setting the DTC

^ The PCM performs this DTC diagnostic continuously.

^ DTCs P0405, P0406, P0102 and P0103 are not set.

^ The Barometric pressure (BARO) is greater than 75 kPa.

^ Must fail 2 of the 5 EGR tests (these test are performed internally by the PCM).

Action Taken When the DTC Sets

^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip 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 Failure Records will store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

^ A history DTC P0101 will clear after 40 consecutive warm-up cycles have occurred without a fault.

^ DTC P0101 can be cleared by using the scan tool Clear Info function.

Diagnostic Aids

Check for the following conditions:

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

^ Plugged intake air duct or 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. If not, check for a restriction.

If DTC P0101 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. This may assist in determining how often the DTC sets.

The Adaptive Learn Matrix (ALM) is used to adjust the EGR vacuum control based on Mass Air Flow (MAF). The ALM may change as a result of back pressure increases over the life of the vehicle or other engine system variations. The ALM is made up of sixteen cells (numbered from zero to fifteen) in which each cell covers a range of engine speed (RPM) and load (mm3).

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

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

5. A voltage reading of less than 4 or over 6V at the MAF sensor signal circuit indicates a fault in the wiring or a poor connection.

6. Verifies that ignition feed voltage and a good ground are available at the MAF sensor.