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 P0100: Mass Air Flow Sensor Circuit Malfunction
DTC P0102: Mass Air Flow Sensor Voltage Low
DTC P0103: Mass Air Flow Sensor Voltage High

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
Ignition Voltage | P0100 | P0100 | P0100 | -- | P0101
MAF Sensor Signal | P0100 | P0102 | P0100 | P0102 | P0101
Low Reference | -- | P0102 | P0100 | -- | P0101

### Circuit/System Description

The mass air flow (MAF) sensor is located in the air intake duct. The MAF sensor is an airflow meter that measures the amount of air that enters the engine. The MAF sensor uses a hot film that is cooled by air flowing past the sensing film as air enters the engine. The amount of cooling is proportional to the amount of the air flow. As the air flow increases greater current is required in order to maintain the hot film at a constant temperature. The engine control module (ECM) uses the MAF sensor in order to provide the correct fuel delivery for all operating conditions.

### Conditions for Running the DTC

• | The engine is operating.

• | The ignition voltage is greater than 10 volts.

• | DTC P0100, P0102 and P0103 run continuously once the above conditions are met for 6 seconds.

### Conditions for Setting the DTC

#### P0100

• | The ECM detects that the MAF sensor signal is 0.0 Hz.

• | The condition exists for 4 seconds or for a cumulative of 30 seconds.

#### P0102

• | The ECM detects that the MAF sensor signal is less than 1135 Hz.

• | The condition exists for 4 seconds or for a cumulative of 30 seconds.

#### P0103

• | The ECM detects that the MAF sensor signal is greater than 15,152 Hz.

• | The condition exists for 4 seconds or for a cumulative of 30 seconds.

### Action Taken When the DTC Sets

DTCs P0100, P0102 and P0103 are type B DTCs.

### Conditions for Clearing the DTC

DTCs P0100, P0102 and P0103 are type B DTCs.

### Diagnostic Aids

• | Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components:

- | The secondary ignition wires or coils

- | Any solenoids

- | Any relays

- | Any motors

• | Inspect for any of the following conditions.

- | A dirty or deteriorating air filter element

- | Water intrusion in the induction system

- | Vacuum leaks

- | Brake booster leaks

- | Faulty crank case ventilation system

- | Restricted or collapsed air duct.

- | An engine mechanical condition

• | Inspect for any contamination, water intrusion, or debris on the sensing elements of the MAF sensor. If debris is present, clean the sensor. If the sensor cannot be cleaned, replace the sensor.

• | A high resistance may cause a driveability concern before this DTC sets.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Air Intake 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. Engine idling for 1 minute, observe the DTC information with a scan tool. DTCs P0100, P0102 and P0103 should not set.
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, disconnect the harness connector at the MAF sensor.
2. Ignition OFF, test for less than 5 Ω between the ground circuit terminal C and ground.

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

Caution: Do NOT use the low reference circuit in the component harness connector for this test. Damage to the control module may occur due to excessive current draw.

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

⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition circuit and replace as necessary.

4. Test for 4.8-5.2 V between the signal circuit terminal A and the ground circuit terminal C.

⇒ | If less than the specified range, test the signal circuit for an open/high resistance or a short to ground. If the circuit/connections test normal, replace the ECM.

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

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

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

8. If all circuits/connections test normal, 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

• | Engine Control Module Replacement for engine control module replacement, setup, and programming