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 (MAF) Sensor Circuit Signal
DTC P0100 09: Mass Air Flow (MAF) Sensor Circuit Rate of Change Above Threshold
DTC P0100 0A: Mass Air Flow (MAF) Sensor Circuit Rate of Change Below Threshold
DTC P0100 26: Mass Air Flow (MAF) Sensor Circuit Frequency Too Low
DTC P0100 27: Mass Air Flow (MAF) Sensor Circuit Frequency Too High
DTC P0101 11: Mass Air Flow (MAF) Sensor Performance Above Maximum Threshold
DTC P0102: Mass Air Flow (MAF) Sensor Circuit Low Frequency
DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency

### 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, more 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 ignition is ON

• | The battery voltage is greater than 8.5 volts

• | The engine speed is between 1,000-4,000 RPM

### Conditions for Setting the DTC

The ECM detects the MAF signal circuit is open, shorted to ground, or shorted to a voltage for less than 1 second.

### Action Taken When the DTC Sets

DTCs P0100, P0101, P0102, and P0103 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0100, P0101, P0102, and P0103 are Type B DTCs.

### Diagnostic Aids

• | Inspect for any contamination, water intrusion, or debris on the sensing elements of the MAF sensor. Certain types of contaminants act as a heat insulator, impairing the response of the sensor to airflow changes. Water or snow can create the opposite effect, and cause the signal to increase rapidly. If a condition is found, clean the sensor. If the sensor cannot be cleaned, replace the sensor.

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

• | 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 cause the MAF sensor signal to be skewed or erratic. Additionally it may cause a rapid fluctuation in the IAT Sensor parameter.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### 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. Verify the harness of the MAF sensor to verify that it is not routed too close to the following components:

• | Any solenoids

• | Any relays

• | Any motors

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

• | Any damaged components

• | Loose or improper installation

• | Restircted exhaust

• | Water intrusion

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

3. Ignition OFF, and the MAIN fuse removed, disconnect the harness connector at the MAF/IAT sensor.
4. Test for less than 5 ohms of resistance between the low reference circuit terminal 2 and ground.

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

Notice: 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.

5. Install the MAIN fuse. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1and ground.

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

6. Test for 4.8-5.2 volts between the signal circuit terminal 4 and ground.

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

7. If all circuits test normal, test or replace the MAF/IAT 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 engine control module replacement, setup, and programming