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 P0102: Mass Air Flow (MAF) Sensor Circuit Low Frequency
DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Ignition 1 Voltage | P0030, P0036, P0102, P0443 | P0101 | P0102 | -- | P0101, P0103
MAF Sensor Signal | P0102 | P0102 | P0102 | P0102 | P0101, P0103, P1101
Ground | -- | P0102 | P0102 | -- | P0102

### 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: 2,000-9,500 Hz
Ignition 1 Voltage | 0 Hz | 0 Hz | --
MAF Sensor Signal | 0 Hz | 0 Hz | 0 Hz
Ground | -- | 0 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. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:

• | Ignition 1 voltage

• | MAF sensor ground

• | MAF sensor signal

• | IAT sensor signal

• | IAT low reference

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies in a range of near 2,000 Hertz at idle to near 9,500 Hertz at maximum engine load.

### Conditions for Running the DTC

• | The engine is running for greater than one second.

• | The engine speed is greater than 300 RPM.

• | The ignition 1 signal is greater than 8 volts.

• | The above conditions are met for greater than 1 second.

• | This DTC runs continuously within the enabling conditions.

### Conditions for Setting the DTC

#### P0102

The ECM detects that the MAF Sensor parameter is less than 10 Hz for greater than 5 seconds.

#### P0103

The ECM detects that the MAF Sensor parameter is greater than 11,000 Hz for greater than 5 seconds.

### Action Taken When the DTC Sets

DTCs P0102 and P0103 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0102 and P0103 are Type B DTCs.

### Diagnostic Aids

• | 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.

• | 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

#### 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. Engine Running, observe the scan tool MAF Sensor parameter. The reading should be between 1,700-3,200 Hz depending on the engine coolant temperature (ECT).
2. 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 190 g/s at the time of the 1-2 shift.
3. 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 air induction system by inspecting for the following conditions:

• | Loose or improper installation

• | Water intrusion

2. Ignition OFF, disconnect the harness connector at the MAF/IAT sensor.
3. Ignition OFF for 90 seconds, test for less than 5 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 the circuits test normal, test or replace the MAF sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Airflow Sensor/Intake Air Temperature Sensor Replacement

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