GSIC - Global Service Information Center

### DTC P0100/31 Mass Air Flow Circuit Malfunction

### DTC P0102/31 Mass or Volume Air Flow Circuit Low Input

### DTC P0103/31 Mass or Volume Air Flow Circuit High Input

## for Preparation Click here

## DESCRIPTION

The Mass Air Flow (MAF) meter measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection time and provide a proper air-fuel ratio. Inside the MAF meter, there is a heated platinum wire exposed to the flow of intake air.
By applying a specific current to the wire, the ECM heats this wire to a given temperature. The flow of incoming air cools the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the voltage applied to these components* in the MAF meter. The voltage level is proportional to the air flow through the sensor. The ECM interprets this voltage as the intake air amount.

HINT:

  *: The circuit is constructed so that the platinum hot wire and temperature sensor provide a bridge circuit, with the power transistor controlled so that the potential of A and B remains equal to maintain the set temperature.

  When any of these DTCs are set, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM, according to the engine rpm and throttle valve position. Fail-safe mode continues until a pass condition is detected.

DTC No. | DTC Detection Condition | Suspected Area

P0100/31

When the MAF meter circuit is open or short for more than 3 seconds

1. Open or short in MAF meter circuit
2. MAF meter
3. ECM

P0102/31

When the MAF meter circuit is open for more than 3 seconds

1. Open in MAF meter circuit
2. MAF meter
3. ECM

P0103/31

When the MAF meter circuit is shorted for more than 3 seconds

1. Short in MAF meter circuit
2. MAF meter
3. ECM

## MONITOR DESCRIPTION

If there is a defect in the MAF meter or an open or short circuit, the voltage level will deviate outside the normal operating range. The ECM interprets this deviation as a defect in the MAF meter and sets a DTC.
Example:
When the sensor voltage output is less than 0.2 V or more than 4.9 V and if either condition continues more than 3 seconds.
This monitor runs for 3 seconds (the first 3 seconds of engine idle) after the engine is started (1 trip detection logic).

HINT:

  When DTC P0100/31, P0102/31 or P0103/31 is detected, check the air-flow ratio by entering the following menus on the intelligent tester: Powertrain / Engine and ECT / Data List / MAF.

Air Flow Value (gm/second) | Malfunction

Approximately 0

1. Open in MAF meter power source circuit
2. Open or short in VG circuit

271.0 or more | Open in EVG circuit

## WIRING DIAGRAM

## INSPECTION PROCEDURE

HINT:

  Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

## When using intelligent tester:

1.READ DATA LIST (MASS AIR FLOW RATE)

1. Connect the intelligent tester to the DLC3.

1. Start the engine.

1. Turn the intelligent tester ON.

1. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.

1. Read the values.

   Result:

     Mass Air Flow Rate (g/second) | Proceed to
     0.0 | A
     271.0 or more | B
     Between 1.0 and 270.0* | C

   HINT:
     *: The value must change when the throttle valve is opened or closed.

| B |

Go to step 6

| C |

CHECK FOR INTERMITTENT PROBLEMS

A |

2.CHECK MASS AIR FLOW METER (POWER SOURCE)

1. Disconnect the A4 MAF meter connector.

1. Turn the ignition switch ON.

1. Measure the voltage of the wire harness side connector.

   Standard voltage:

     Tester Connection | Specified Condition
     A4-1 (+B) - Body ground | 9 to 14 V

| NG |

Go to step 5

OK |

3.CHECK ECM (VG VOLTAGE)

1. Start the engine.

1. Measure the voltage of the ECM connector.

   HINT:
     The shift lever position should be N and the A/C switch should be turned OFF.

   Standard voltage:

     Tester Connection | Condition | Specified Condition
     E11-28 (VG) - E11-30 (E2G) | Engine is idling | 0.5 to 3.0 V

| OK |

REPLACE ECM

NG |

4.CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)

1. Disconnect the A4 MAF meter connector.

1. Disconnect the E11 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     A4-3 (VG) - E11-28 (VG) | Below 1 Ω
     A4-2 (E2G) - E11-30 (E2G) | Below 1 Ω
     A4-3 (VG) or E11-28 (VG) - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

REPLACE MASS AIR FLOW METER

5.CHECK WIRE HARNESS (MASS AIR FLOW METER - MAIN RELAY)

1. Disconnect the A4 MAF meter connector.

1. Disconnect the 1J integration relay connector from the engine room junction block (Click here).

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     A4-1 (+B) - 1J-5 | Below 1 Ω
     A4-1 (+B) or 1J-5 - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

INSPECT ECM POWER SOURCE CIRCUIT

6.CHECK ECM (SENSOR GROUND)

1. Measure the resistance of the E11 ECM connector.

   Standard resistance:

     Tester Connection | Specified Condition
     E11-30 (E2G) - Body ground | Below 1Ω

| NG |

REPLACE ECM

OK |

7.CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)

1. Disconnect the A4 MAF meter connector.

1. Disconnect the E11 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     A4-3 (VG) - E11-28 (VG) | Below 1 Ω
     A4-2 (E2G) - E11-30 (E2G) | Below 1 Ω
     A4-3 (VG) or E11-28 (VG) - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

REPLACE MASS AIR FLOW METER

## When not using intelligent tester:

1.CHECK ECM (VG VOLTAGE)

1. Start the engine.

1. Measure the voltage of the ECM connector.

   HINT:
     The shift lever position should be N and the A/C switch should be turned OFF.

   Standard voltage:

     Tester Connection | Condition | Specified Condition
     E11-28 (VG) - E11-30 (E2G) | Engine is idling | 0.5 to 3.0 V

| OK |

REPLACE ECM

NG |

2.CHECK MASS AIR FLOW METER (POWER SOURCE)

1. Disconnect the A4 MAF meter connector.

1. Turn the ignition switch ON.

1. Measure the voltage of the wire harness side connector.

   Standard voltage:

     Tester Connection | Specified Condition
     A4-1 (+B) - Body ground | 9 to 14 V

| NG |

Go to step 4

OK |

3.CHECK WIRE HARNESS (MASS AIR FLOW METER - ECM)

1. Disconnect the A4 MAF meter connector.

1. Disconnect the E11 ECM connector.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     A4-3 (VG) - E11-28 (VG) | Below 1 Ω
     A4-2 (E2G) - E11-30 (E2G) | Below 1 Ω
     A4-3 (VG) or E11-28 (VG) - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

REPLACE MASS AIR FLOW METER

4.CHECK WIRE HARNESS (MASS AIR FLOW METER - MAIN RELAY)

1. Disconnect the A4 MAF meter connector.

1. Disconnect the 1J integration relay connector from the engine room junction block.

1. Measure the resistance of the wire harness side connectors.

   Standard resistance:

     Tester Connection | Specified Condition
     A4-1 (+B) - 1J-5 | Below 1 Ω
     A4-1 (+B) or 1J-5 - Body ground | 10 kΩ or higher

| NG |

REPAIR OR REPLACE HARNESS AND CONNECTOR

OK |

INSPECT ECM POWER SOURCE CIRCUIT