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 P0101: Mass Air Flow (MAF) Sensor Performance
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 | P0102 | P0102 | -- | P0101
MAF Sensor Signal | P0102 | P0102 | P0102 | P0103 | P0101
Low Reference | -- | P0103 | P0103 | -- | P0101

### Typical Scan Tool Data

#### MAF Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: 3-4 g/s, 0.6-0.9 V
Ignition 1 Voltage | 0.g/s, 0 V | 0 g/s, 0 V | --
MAF Sensor Signal | 0 g/s, 0 V | 0 g/s, 0 V | 196 g/s, 5 V
Low Reference | 3.9 g/s, 0.7 V | 196 g/s, 5 V | *
* Internal ECM damage may occur if the circuit is shorted to B+.

### Circuit/System Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The control module 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 control module applies a voltage to the sensor on the signal circuit. The sensor uses the voltage to produce a frequency based on the inlet air flow through the sensor bore. The frequency varies within a range of near 2,000 Hertz at idle to near 10,000 Hertz at maximum engine load.

### Conditions for Running the DTC

#### P0101

• | DTCs P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0221, P0222, or P0223 are not set.

• | The engine speed is between 512-4,512 RPM.

• | The TP indicated angle is between 15-100 percent.

• | DTC P0101 runs continuously once the above conditions are met.

#### P0102 and P0103

• | The engine speed is greater than 512 RPM.

• | The TP indicated angle is less than 1 degrees.

• | DTCs P0102 and P0103 run continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0101

The engine control module (ECM) detects that the MAF sensor signal is not within a predetermined range of the calculated MAF value.

#### P0102

The ECM detects that the MAF sensor signal is less than 0.2 volt.

#### P0103

The ECM detects that the MAF sensor signal is greater than 4.9 volts.

### Action Taken When the DTC Sets

• | DTC P0101 is a Type B DTC.

• | DTCs P0102 and P0103 are Type A DTCs.

### Conditions for Clearing the DTC

• | DTC P0101 is a Type B DTC.

• | DTCs P0102 and P0103 are Type A 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

• | 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 3-10 g/s at idle to 150 g/s or greater at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.

• | 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

#### 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 running for 1 minute, verify the scan tool MAF sensor voltage parameter is between 0.5-0.9 volts.
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 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. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for battery voltage on the ignition 1 voltage circuit terminal 3.

⇒ | If less than B+, repair the open/high resistance in the ignition 1 voltage circuit.

4. Verify the scan tool MAF sensor voltage parameter is less than 1 volt.

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

5. Connect a test lamp between the ignition 1 voltage circuit terminal 3 and the signal circuit terminal 2. Verify the scan tool MAF sensor voltage parameter is greater than 4.8 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.

6. If all circuits test normal, test or replace the MAF sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the MAF sensor.
2. Install 3 jumper wires between the harness connector and the MAF sensor.
3. Ignition ON, measure for voltage on the MAF signal circuit when blowing air through the MAF sensor.

⇒ | If the signal voltage did not increase with air flow, replace the MAF sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Mass Air Flow (MAF) Sensor Replacement

• | Control Module References for control module replacement, setup, and programming