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 Descriptor

DTC P0101: Mass Air Flow (MAF) Sensor Circuit Performance

### 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, 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

• | Before the ECM can report DTC P0101 failed, DTCs P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0100, P0102, P0103, P0111, P0112, P0113, P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0338, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095, P2227, P2228, or P2229 must run and pass.

• | DTC P2176 is not set.

• | The engine is operating for greater than 1 second.

• | The MAF sensor signal is greater than 1 grams per second.

• | The ignition voltage is greater than 10 volts.

• | The engine coolant temperature (ECT) is greater than 10°C (50°F).

• | The long term fuel trim is enabled.

• | The throttle angle is steady +/-2 percent.

• | The ECM detects greater than 150 revolutions of the crankshaft.

• | DTC P0101 runs continuously once the above conditions are met for greater than 5 seconds.

### Conditions for Setting the DTC

• | The ECM detects that the MAF sensor signal is greater or less than the calculated air flow based on engine load and engine speed.

| OR

• | The ECM detects that the MAF sensor signal is greater or less than the calculated air flow, and The ECM detects a significant error in the long term fuel trim at cruising speed.

### Action Taken When the DTC Sets

DTC P0101 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P0101 is a Type B DTC.

### 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 the hydro-carbon (HC) absorber in the air cleaner assembly for ruptures that would leak charcoal into the air intake, contaminating the sensing element.

• | 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

### Circuit/System Verification

1. Engine idling for 1 minute, observe the DTC information with a scan tool. DTC P0101 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. Inspect for the following conditions:

• | An engine vacuum leak

• | An air leak in the intake air duct between the mass air flow (MAF) sensor and the throttle body

• | A plugged or collapsed intake air duct

• | Objects that block the MAF sensor air inlet

• | An air filter element that is restricted

• | The hydro-carbon absorber in the air cleaner assembly for ruptures or deterioration.

• | A restricted throttle plate or for carbon build-up around the throttle plate

• | An unseated engine oil dip stick

• | A loose or missing engine oil fill cap

• | An over filled crankcase

⇒ | If you find any of the above conditions, repair as necessary.

2. Ignition OFF, disconnect the harness connector at the MAF sensor.

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, load test the ignition circuit for B+ between terminal B and ground.

⇒ | If less than the specified value, repair the ignition circuit for an open/high resistance.

4. Test for less than 5 Ω between the ground circuit terminal C and the battery ground.

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

5. Test for less than 5.10 V between the signal circuit terminal A and ground circuit terminal C.

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

6. Test for greater than 3.98 mA between the signal circuit terminal A and the ground circuit terminal C.

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

7. 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/Intake Air Temperature Sensor Replacement

• | Control Module References for engine control module (ECM) replacement, setup, and programming