P0101

DTC P0101 MAF System Performance




Circuit Description
The mass air flow (MAF) sensor measures the amount of air which passes through it into the engine during a given time. The powertrain control module (PCM) uses the mass air flow information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity or air indicates deceleration or idle.

The MAF sensor produces a frequency signal which can be monitored using a scan tool. The frequency will vary within a range of around 4 to 7 g/s, at idle to around 25 to 40 g/s at maximum engine load. DTC P0101 will be set if the signal from the MAF sensor does not match a predicted value based on throttle position and engine RPM.

Conditions for Setting the DTC
- The engine is running.
- No TP sensor or MAP sensor DTCs are set.
- The throttle is steady, TP angle doesn't change by more than 1%.
- System voltage is between 11.5 volts and 16 volts.
- Calculated air flow is between 25 g/second and 40 g/second.
- Above conditions present for at least 1 second.
- MAF signal frequency indicates an airflow significantly higher or lower than a predicted value based on throttle position and engine RPM for a total of 12.5 seconds over a 25-second period of time.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which the fault is detected.
- The PCM calculates an airflow value based on idle air control valve position, throttle position, RPM and barometric pressure.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.

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 or by disconnecting the PCM battery feed.

Diagnostic Aids
An intermittent may be caused by the following:
- Poor connections.
- Mis-routed harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.
Refer to Intermittents under service category Symptoms.

Any un-metered air may cause this DTC to set. Check for the following:
- The duct work at the MAF sensor for leaks.
- 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.

Steps 1 - 3:

Steps 4 - 10:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart.
2. The MAF system performance or rationality diagnostic uses the MAP sensor signal along with other input 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 verify that the MAP sensor is working properly.
6. Verifies the signal circuit from the MAF sensor electrical connector to the PCM. Verifies whether a ground and B+ circuit is available.