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 Descriptor

DTC P0101: Mass Air Flow (MAF) Sensor Performance

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Ignition 1 Voltage | P0031, P0037, P0100, P0458 | P0100 | P0100 | -- | P0100
MAF Sensor Signal | P0100 | P0100 | P0100 | P0100 | P0101, P0102, P0103
Ground | -- | P0100 | P0100 | -- | P0100

### Typical Scan Tool Data

#### MAF Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine Running at various operating conditions Parameter Normal Range: 1,700-12,500 Hz
Ignition 1 Voltage | 65,535 Hz | 65,535 Hz | --
MAF Sensor Signal | 65,535 Hz | 65,535 Hz | 65,535 Hz
Ground | -- | 65,535 Hz | --

### Circuit/System Description

The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. The MAF/IAT sensor has the following circuits:

• | Ignition 1 voltage

• | MAF sensor ground

• | MAF sensor signal

• | IAT sensor signal

• | IAT low reference

The purpose of this diagnostic is to analyze the performance of the MAF sensor by comparing the measured airflow to the following 2 distinct models:

• | The first model is separated into two parts. The first part is based on basic engine parameters and uses engine speed, and throttle angle as inputs. The second part is derived from long term fuel trim, at cruising speed and the ECM is looking for an adaptation value to be within a calibrated range.

• | The second model uses the manifold absolute pressure (MAP) sensor for input, and the ECM is looking for an adaptation value to be within a calibrated range.

### Conditions for Running the DTC

• | DTCs P0010, P0011, P0013, P0014, P0096, P0097, P0098, P0099, P0100, P0102, P0103, P0106, P0107, P0108, P0121, P0122, P0123, P0221, P0222, P0223, P0236, P0237, P0238, P0335, P0336, P2088, P2089, P2090, P2091, P2176, P2227, P2228, or P2229 is not set.

• | The engine is running.

• | The engine coolant temperature (ECT) is warmer than 10°C (50°F).

• | The ignition 1 voltage signal is greater than 10.5 volts.

• | The change in the throttle position (TP) is less than 2 percent.

• | The charge air bypass valve is closed.

• | Long term cruise fuel trim needs to be active and stable.

• | This DTC runs continuously within the enabling conditions.

### Conditions for Setting the DTC

• | The ECM detects that the measured MAF is not within range of the calculated airflow based on throttle angle and engine speed.

| AND

• | The ECM detects a significant error in the long term fuel trim at cruising speed.

| OR

• | The ECM detects that the measured MAF is not within range of the calculated model that is derived from MAP.

### Action Taken When the DTC Sets

• | DTC P0101 is a Type B DTC.

• | The ECM will disable boost control, and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.

### Conditions for Clearing the MIL/DTC

DTC P0101 is a Type B DTC.

### Diagnostic Aids

• | The charge air cooler (CAC) is connected to the turbocharger and to the throttle body by flexible ductwork that requires the use of special high torque fastening clamps. These clamps cannot be substituted. In order to prevent any type of air leak when servicing the ductwork, the tightening specifications and proper positioning of the clamps is critical and must be strictly adhered to.

• | Use a solution of dish soap and water in a spray bottle to pinpoint any suspected air leaks in the induction system and in the CAC assembly.

• | A steady or intermittent high resistance of 15 ohms or greater on the ignition 1 voltage circuit will cause the MAF sensor signal to be increased by as much as 60 g/s.

• | Certain types of contaminants on the MAF sensor heating elements act as a heat insulator, which will impair the response of the sensor to airflow changes. This condition will affect the Long Term Fuel Trim adaptation value.

• | Depending on the current ambient temperature, and the vehicle operating conditions, a MAF sensor signal circuit that is shorted to the IAT signal circuit will increase or decrease the MAF sensor signal that is interpreted by the ECM. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Turbocharger System Description

• | Boost Control System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

#### Special Tools

J 38522 Variable Signal Generator

### Circuit/System Verification

1. Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust.
2. Verify that an exhaust leak does not exist, including the mating surface area between the turbocharger and the exhaust manifold.
3. Ignition OFF for 90 seconds, determine the current vehicle testing altitude.
4. Ignition ON, engine OFF, observe the scan tool BARO parameter, Boost Pressure Sensor parameter, and MAP Sensor parameter. Compare the parameters to the Altitude Versus Barometric Pressure table. The parameters should be within the specified range indicated in the table.
5. Engine operating at idle, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz.
6. 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 2-6 g/s at idle to greater than 200 g/s at the time of the 1-2 shift.
7. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

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

• | Any damaged components

• | Loose or improper installation

• | An air flow restriction

• | Vacuum leaks

• | A turbocharged air leak

• | Improperly routed vacuum hoses

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

• | Inspect the MAF sensor elements for contamination

2. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
3. Ignition OFF for 90 seconds, test for less than 5.0 ohms between the ground circuit terminal B and ground.

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

4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C 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 signal circuit terminal A and ground.

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

6. Ignition OFF, connect the red lead of the J 38522 to the signal circuit terminal A at the MAF/IAT sensor harness connector. Connect the battery voltage supply to B+. Connect the black lead to ground.
7. Set the J 38522 Signal switch to 5 volts, the Frequency switch to 5K, and the Duty Cycle switch to Normal.
8. Engine Idling, observe the scan tool MAF Sensor parameter. The scan tool MAF Sensor parameter should be between 4,950-5,025 Hz.

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

9. If all circuits test normal, test or replace the MAF sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor Replacement

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