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 Voltage
DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Voltage

### 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 | P0103 | 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: 0.5-4.3 Volts
Ignition 1 Voltage | 0 Volts | 0 Volts | --
MAF Sensor Signal | 0 Volts | 0 Volts | 4.5-5.0 Volts
Ground | -- | 0 Volts | --

### 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 MAF sensor used on this engine is a voltage based sensor. The greater the airflow, the greater the voltage signal. 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

• | A shared MAF/IAT low reference

• | MAF sensor signal

• | IAT sensor signal

### Conditions for Running the DTCs

• | DTC P0335 or P0336 is not set.

• | The engine is running.

• | The engine speed is greater than 736 RPM.

• | The ignition 1 voltage is greater than 10 volts.

• | The throttle position (TP) is greater than 2 percent.

• | These DTCs runs continuously within the enabling conditions.

### Conditions for Setting the DTCs

#### P0102

The ECM detects that the MAF sensor signal is less than 0.50 volt for greater than 2 seconds.

#### P0103

The ECM detects that the MAF sensor signal is greater than 4.30 volts for greater than 2 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

• | 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 voltage signal.

• | At ignition ON, engine OFF, a small amount of voltage will display on the scan tool MAF sensor parameter. This is due to the heat that is generated by the MAF sensor heating elements.

• | 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

### Circuit/System Verification

1. A wide open throttle (WOT) acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly.
2. 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. Ignition OFF, verify the integrity of the air induction system by inspecting for the following conditions:

• | Damage to the MAF sensor

• | Loose or improper installation

• | An air flow restriction

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

• | Inspect the MAF sensor elements for contamination

2. Ignition OFF for 90 seconds, disconnect the harness connector at the MAF/IAT sensor.
3. Test for less than 5 ohms between the low reference circuit terminal 1 and ground.

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

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

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

5. Verify the scan tool MAF Sensor parameter is less than 0.50 volt.

⇒ | If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the ECM.

6. Ignition ON, connect a test lamp between B+ and the signal circuit terminal 3.
7. Verify the scan tool MAF Sensor parameter is greater than 4.3 volts.

⇒ | 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.

8. If the circuits test normal, 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