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 | P0102 | P0101 | P0102 | P0690 | P0101, P0103
MAF Sensor Signal | P0102 | P0102 | P0102 | P0102 | P0101, P0103
Ground | -- | P0102 | P0102 | -- | P0102

### Typical Scan Tool Data

#### Mass Air Flow Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine running Parameter Normal Range: 850-14,500 Hz
Ignition 1 Voltage | 0 Hz | 0 Hz | --
MAF Sensor Signal | 0 Hz | 0 Hz | 0 Hz
Ground | -- | 0 Hz | --

### Circuit 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

• | The ground circuit

• | A MAF sensor signal circuit

• | An IAT sensor signal circuit

• | Low reference circuit

The ECM applies 5 volts to the MAF sensor signal circuit on the MAF sensor. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency is near to 850 Hz at idle, and near to 14,500 Hz at maximum engine load

### Conditions for Running the DTC

• | The engine is running for more than 1 second.

• | The engine speed is more than 300 RPM.

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

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

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

### Conditions for Setting the DTC

#### P0102

• | The ECM detects that the MAF sensor parameter is less than 850 Hz.

• | It occurs 50 times during the 63 tests.

• | DTC P0102 sets when the above conditions are met.

#### P0103

• | The ECM detects that the MAF sensor parameter is more than 14,500 Hz.

• | It occurs 50 times during the 63 tests.

• | DTC P0103 sets when the above conditions are met.

### Action Taken When the DTC Sets

DTCs P0102 and P0103 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0102 and P0103 are Type B DTCs.

### Diagnostic Aids

• | 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 380 g/s or more at the time of the 1-2 shift.

• | Verify that any electrical aftermarket devices are properly connected and grounded. Refer to Checking Aftermarket Accessories .

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Controls Connector End Views

• | Engine Control Module Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

#### Special Tools

J 38522 Variable Signal Generator

### Circuit/System Verification

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

• | Damaged components

• | Loose or improper installation

• | Restricted air flow

• | Vacuum leak

• | Water intrusion

### Circuit/System Testing

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

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

4. Ignition ON, verify the test lamp illuminates between the ignition switch circuit 1 terminal C and ground.

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

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

### Component Testing

Important: You must perform the Circuit/System Testing before proceeding with Component 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/Intake Air Temperature Sensor Replacement

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