P0101

DTC P0101

CIRCUIT DESCRIPTION
The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), manifold absolute pressure (MAP), and the throttle position (TP) sensor. This is an explicit model-based diagnostic containing three separate models for the intake system.
- One model, the throttle model, describes the flow through the throttle body and is used to estimate the mass air flow through the throttle body as a function of barometric pressure (BARO), throttle position, intake air temperature (IAT), and estimated manifold absolute pressure.
- Another model, the first intake manifold model, describes the intake manifold and is used to estimate manifold absolute pressure as a function of the mass air flow into the manifold from the throttle body and from the exhaust gas recirculation (EGR) valve, and the mass air flow out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the mass air flow estimate calculated from the above throttle model.
- The third model is the second intake manifold model and is identical to the first intake manifold model except that the MAF sensor measurement is used instead of the throttle model estimate for the throttle air input.
- Finally, a fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model.




The estimates of mass air flow and manifold absolute pressure obtained from this system of models and calculations are then compared to the actual measured values from the MAF, MAP, and the TP sensor and to each other to determine the appropriate DTC to fail. The table illustrates the possible failure combinations and the resulting DTC or DTCs.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0101 Mass Air Flow (MAF) Sensor Performance

CONDITIONS FOR RUNNING THE DTC
- DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0335, P0336, P0385, P0386, P0401, P0405, P1404 are not set.
- The engine speed is between 500-6,700 RPM.
- The IAT Sensor parameter is between -7 and +60°C (19-140°F).
- The ECT Sensor parameter is between 70-121°C (158-250°F).
- This DTC runs on a 12.5 ms loop.
- This DTC runs continuously within the enabling conditions.

CONDITIONS FOR SETTING THE DTC
The powertrain control module (PCM) detects that the actual measured air flow from MAF, MAP, EGR, and TP is not within range of the calculated air flow that is derived from the system of models for more than 0.5 second.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-10 g/s at idle to 220 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
- A skewed or stuck engine coolant temperature (ECT) or IAT sensor will cause the calculated models to be inaccurate and may cause this DTC to run when it shouldn't.
- A steady or intermittent high resistance of 15 ohms or more on the ignition 1 voltage circuit will cause the MAF sensor values to be skewed high by up to 60 g/s, and may cause this DTC to set. A high resistance will cause a driveability concern before this DTC sets.
- The barometric pressure (BARO) that is used to calculate the air flow models is initially based on the MAP sensor at key ON. When the engine is running the BARO value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. The value shown for the MAP sensor parameter varies with the altitude. With the ignition ON and the engine OFF, 101 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1,000 feet) of altitude.
- A high resistance on the low reference circuit of the MAP sensor and the TP sensor at the same time may cause this DTC to set.
- If the condition is intermittent, refer to Inducing Intermittent Fault Conditions in Diagnostic Aids and Intermittent Conditions. Diagnostic Strategies

TEST DESCRIPTION

Steps 1-4:

Steps 5-9:

Steps 10-14:

Steps 15-21:

Steps 22-25:

The numbers below refer to the step numbers on the diagnostic table.
4. This step will determine if any mechanical faults have caused this DTC to set.
12. This voltage drop test will determine if high resistance has caused this DTC to set.
14. This step verifies the voltage signal from the PCM to the MAF sensor connector.
15. This step will determine if the PCM can accurately process the frequency signal that it receives from the MAF sensor.
16. This step will determine if an abnormal resistance of less than 1,150 ohms has skewed the MAF sensor frequency signal.