The intake flow rationality diagnostic provides the within-range rationality check for the mass air flow (MAF), the manifold absolute pressure (MAP), and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing 4 separate models for the intake system.

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

P0101

The engine control module (ECM) detects that the difference between the measured MAF and the MAP performance test 2 is greater than 25 g/s for greater than 0.5 second.

P1101

The engine control module (ECM) detects that the actual measured airflow from the MAF, the MAP, and the TP sensors is not within range of the calculated airflow that is derived from the system of models for more than 0.5 second.

DTCs P0101 and P1101 are Type B DTCs.

DTCs P0101 and P1101 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 38522 Variable Signal Generator

1. Verify the integrity of the entire air induction system by inspecting for the following conditions:

•	Any damaged components

•	Loose or improper installation

•	An air flow restriction

•	An air flow leak

•	Any vacuum leak

•	In cold climates, inspect for any snow or ice buildup

•	Water intrusion

2. Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust .

Caution: Refer to Road Test Caution in the Preface section.

3. Road test the vehicle and verify that the MAF sensor calculated g/s and the actual MAF g/s parameters are near or equal to each other.
4. A skewed MAF sensor, intake air flow restriction or intake air flow leak after the MAF sensor may cause the calculated g/s and MAF g/s parameters to disagree. Road test the vehicle while observing both parameters under various engine loads.
5. 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 3-8 g/s at idle to 190 g/s or more at the time of the 1-2 shift.
6. The BARO that is used by the ECM to calculate the air flow models is initially based on the MAP sensor at ignition ON. When the engine is running, the ECM will continually update the BARO value near WOT using the MAP sensor and a calculation. A skewed MAP sensor will cause the BARO value to be inaccurate. Use the scan tool to compare the BARO parameter at ignition ON to the Altitude vs. Barometric Pressure table. Determine the altitude for your area and refer to Altitude Versus Barometric Pressure .
7. Engine running, observe the DTC information with a scan tool. DTCs P0101 or P1101 should not set.
8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
2. Ignition OFF, allow at least 60 seconds for the control module to power down.
3. Test for less than 2 ohms of resistance between the MAF ground circuit terminal C and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

4. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal B and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

5. Ignition ON, test for 4.8-5.2 volts between the MAF signal circuit terminal A and ground.

⇒	If less than the specified range, test the signal circuit for a short to round or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

6. Ignition OFF, connect the J 38522 to the vehicle. Refer to Component Testing for instructions.

To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522 to the vehicle as follows:

1. Ignition OFF, connect the battery voltage supply and ground the black lead.
2. Connect the red lead to the signal circuit of the MAF sensor.
3. Set the duty cycle switch to Normal.
4. Set the Frequency switch to 5 K.
5. Set the signal switch to 5 volts.
6. Engine running, observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.

⇒	If the MAF Sensor parameter is not within the specified range, replace the ECM.

⇒	If the MAF Sensor parameter is within the specified range, replace the MAF sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.