For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0101: Mass Air Flow (MAF) Sensor Performance
DTC P1101: Intake Air Flow System Performance

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Ignition 1 Voltage | P0102 | P0101 | P0102 | -- | P0101, P0103
MAF Sensor Signal | P0102 | P0102 | P0102 | P0223 | P0101, P0103, P1101
Ground | -- | P0102 | P0102 | -- | P0102

### Typical Scan Tool Data

#### Mass Air Flow Sensor

Circuit | Normal Range | Short to Ground | Open | Short to Voltage
--- | --- | --- | --- | ---
Ignition 1 Voltage | -- | 0 Hz | 0 Hz | --
MAF Sensor Signal | 850-14,500 Hz | 0 Hz | 0 Hz | 0 Hz
Ground | -- | -- | 0 Hz | --

### 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) sensors. This is a displayed model based on diagnosis containing 4 separate models for the intake system.

• | The throttle model describes the flow through the throttle body and is used to estimate the MAF through the throttle body as a function of barometric pressure (BARO), TP, intake air temperature (IAT), and estimated MAP. The information of this model is displayed on the scan tool as the MAF performance test parameter.

• | The first intake manifold model describes the intake manifold and is used to estimate MAP as a function of the MAF into the manifold from the throttle body and the MAF out of the manifold caused by engine pumping. The flow into the manifold from the throttle uses the MAF estimate calculated from the above intake manifold model. The information of this model is displayed on the scan tool as the MAP performance test 1 parameter.

• | The only difference between the second intake manifold model and the first intake manifold model is that the second one uses MAF sensor measurement, not the throttle air flow estimated by the throttle model. The information of this model is displayed on the scan tool as the MAP performance test 2 parameter.

• | The fourth model is created from the combination and additional calculations of the throttle model and the first intake manifold model. The information of this model is displayed on the scan tool as the TP performance test parameter.

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, 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.

MAF Performance Test | MAP Performance Test 1 | MAP Performance Test 2 | TP Performance Test | DTCs Passed | DTCs Failed
--- | --- | --- | --- | --- | ---
X | X | OK | OK | P0101, P0106, P0121, P1101 | None
OK | OK | Fault | OK | P0101, P0106, P0121, P1101 | None
Fault | OK | Fault | OK | P0106, P0121, P1101 | P0101
OK | Fault | Fault | OK | P0101, P0121, P1101 | P0106
Fault | Fault | Fault | OK | P0121, P1101 | P0101, P0106
X | X | OK | Fault | P0101, P0106, P1101 | P0121
OK | OK | Fault | Fault | P0101, P0106, P0121, P1101 | None
Fault | OK | Fault | Fault | P0101, P0106, P0121 | P1101
X | Fault | Fault | Fault | P0101, P0106, P0121 | P1101

### Conditions for Running the DTC

• | DTCs P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0128, P0335, P0336, P0401, P0405, P1404 are not set

• | The engine speed is between 550-5,000 RPM.

• | The IAT sensor parameter at -7 to +60°C (+19 to +140°F).

• | The ECT sensor parameter at 70-129°C (158-264°F).

• | The DTCs run continuously when the conditions are met.

### Conditions for Setting the DTC

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.

### Action Taken When the DTC Sets

DTCs P0101 and P1101 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0101 and P1101 are Type B DTCs.

### Diagnostic Aids

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

• | 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.

• | 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.

• | 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 1.5 g/s at idle to 190 g/s or more at the time of the 1-2 shift.

• | A steady or intermittent high resistance of 25 ohms or higher on the ignition 1 voltage circuit will cause the MAF sensor values to be skewed high by up to 30 g/s. Use a scan tool and compare the MAF sensor parameter with a known good vehicle under various operating conditions.

• | 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 should not. Refer to Temperature Versus Resistance.

• | The BARO that is used by the ECM to calculate the air flow models is initially based on the MAP sensor value at ignition ON. When the engine is running, the ECM will continually update the BARO value near wide open throttle (WOT) using the MAP sensor and a calculation. A skewed MAP sensor will cause the BARO value to be inaccurate. Use a scan tool and compare the BARO parameter with the ignition ON to the Altitude Versus Barometric Pressure table. Determine the altitude for your area and refer to the Altitude Versus Barometric Pressure.

• | A skewed MAP sensor will also cause the first and second intake manifold models calculated to disagree with the actual MAP sensor measurements. Use a scan tool and compare the MAP Sensor parameter to a known good vehicle under various operating conditions.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Special Tools

J 38522 Variable Signal Generator

### Circuit/System Verification

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

• | 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. Turn the ignition ON, observer 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 difference between the TP sensor 1 and the sensor 2 parameters is more than 4 percent, refer to DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the MAF sensor.
2. Turn the ignition OFF, allow sufficient time for the control module to power down. Test for less than 5 ohms 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 short to ground or open/high resistance. If the circuit test normal, replace the ECM.

⇒ | If the circuit test normal, replace the ECM.

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

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

5. J 38522 refer to Component Testing.

### Component Testing

Note: You must perform the Circuit/System Verification before proceeding with Components 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 the ignition OFF.
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 5K.
6. Set the signal switch to 5 volts.
7. Start the engine and 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.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor with Intake Air Temperature Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming