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.

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.

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

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Special Tools Required

J 38522 Variable Signal Generator

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

•	A restricted or collapsed air intake duct

•	A misaligned or damaged air intake duct

•	A dirty or deteriorating air filter element

•	Any objects blocking the air inlet probe of the MAF/IAT sensor

•	Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor

•	Any water intrusion in the induction system

•	Any vacuum leak downstream of the MAF/IAT sensor

•	An intake manifold leak

•	A MAP sensor seal that is missing or damaged

•	A BARO sensor that is skewed or stuck

•	A skewed or stuck ECT or IAT sensor-refer to Temperature Versus Resistance .

•	Any type of restriction in the exhaust system-Refer to Restricted Exhaust .

2. Ignition ON, observe the MAP Sensor parameter with a scan tool. Start the engine. The MAP Sensor parameter should decrease.

⇒	If the MAP Sensor kPa parameter does not decrease, refer to DTC P0106 .

3. Ignition ON, depress the accelerator pedal completely and observe the TP Indicated Angle parameter with a scan tool. The TP Indicated Angle parameter should read 98-100 percent.

⇒	If the TP Indicated Angle parameter is not within the specified range, refer to DTC P1516, P2101, P2119, or P2176 .

4. Ignition ON, perform a snapshot of the throttle actuator control (TAC) data while performing the following action. Refer to Scan Tool Snapshot Procedure .

•	Slowly depress the accelerator pedal to WOT position, then slowly release the pedal. Exit from the snapshot and review the data.

•	Compare the TP Sensor 1 and the TP Sensor 2 parameters, frame by frame. The difference between the parameters should be less than 4 percent.

⇒	If the TP Sensor 1 and Sensor 2 parameter difference is more than 4 percent, refer to DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135 .

5. Engine running, observe the DTC information with a scan tool. DTCs P0101 or P1101 should not set.
6. 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 sensor.
2. Ignition OFF, allow sufficient time for the ECM to power down. Test for less than 5 ohms of resistance between the low reference circuit terminal D and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

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

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

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

4. Ignition ON, verify that a test lamp illuminates between the MAF sensor 12-volt reference voltage circuit terminal C and ground.

⇒	If the test lamp does not illuminate, test the 12-volt reference circuit for a short to ground or an open/high resistance.

5. Connect the J 38522 to the vehicle. Refer to Component Testing.

Important: You must complete the Circuit/System Testing before proceeding with Component/System Testing.

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

1. Turn OFF the ignition.
2. Connect the battery voltage supply and ground the black lead.
3. Connect the red lead to the signal circuit terminal A of the MAF sensor.
4. Set the duty cycle switch to Normal.
5. Set the frequency switch to 5 K.
6. Set the signal switch to 5 volts.
7. Start the engine, 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.