For 1990-2009 cars
Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The mass air flow (MAF) sensor measures the amount of air which passes through the sensor in a given amount of time. The powertrain control module (PCM) uses this information to determine the operating requirements of the engine in order to control fuel delivery. The PCM calculates the engines fuel requirements by monitoring the current flow on the signal wire from the mass air flow (MAF) sensor. When the volume of air entering the MAF sensor increases, the current flow seen by the PCM from the MAF sensor also increases. When the air flow decreases, the current seen by the PCM also decreases. The MAF sensor is located between the air intake tube and the air cleaner in the RH front area of the engine compartment.

### Conditions for Running the DTC

The ignition is ON or the engine is running.

### Conditions for Setting the DTC

• | The MAF sensor output current is more than 4.9 mA.

• | The condition is present for more than 5 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

• | The PCM enters the Failsafe mode and determines the injector drive time and the idle air control (IAC) duty cycle according to the TP sensor input and the engine speed. The EGR valve operation is stopped.

### Conditions for Clearing the MIL/DTC

• | The MIL turns off after 3 consecutively passing cycles without a fault present.

• | A History DTC will clear after 40 consecutive warm-up cycles without a fault.

• | Perform the scan tool clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

Check for any of the following conditions:

• | The MAF sensor readings vary with the air temperature and the barometric pressure (BARO). The specifications indicated are at 20°C (68°F) and at sea level.

• | A misrouted wiring harness. Inspect the MAF sensor harness to ensure that the harness is not routed too close to high voltage wires such as spark plug leads.

• | A damaged wiring harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the connectors and the wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the fault.

• | Check for a plugged intake air duct or a dirty air filter element. An acceleration from a stop should cause the MAF displayed on the scan tool to increase from about 2.0 to 3.5 g/s at idle to 5 to 9 g/s at 2,500 RPM.

If a DTC P0103 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0103 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0103 appears in the Not Ran Since Code Cleared list, the P0103 diagnostic has not yet run. When the DTC P0103 does not appear in the Not Ran Since Code Cleared list, the P0103 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the P0103 diagnostic has passed. DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect the wiring harness and components for any of the following conditions:

• | Any backed-out terminals

• | Any improper mating of terminals

• | Any broken electrical connector locks

• | Any improperly formed or damaged terminals

• | Any faulty terminal-to-wire connections

• | Any physical damage to the wiring harness

• | A broken wire inside the insulation

• | Any corrosion of the electrical connections, the splices, or the terminals

If the DTC P0103 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step will determine if the fault is present.

3. Review Freeze Frame data to determine when the DTC set. Always record this information.

4. Normal voltage at idle for the MAF sensor signal circuit should be 1.6 volts to 2.0 volts. This voltage reading should increase steadily to 5 volts when engine speed is increased to approximately 4,000 RPM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Start the engine.
2. Install a scan tool.
3. With the throttle closed, select the mass air flow (MAF) sensor parameter on the scan tool.

Is the MAF more than the specified value?

2.0--3.5 g/s

Go to Step 4

Go to Step 3

3 |

1. Turn ON the ignition, leaving the engine off.
2. Perform the scan tool Clear DTC Information function.
3. Operate the vehicle within the Freeze Frame conditions as noted.

Is DTC P0103 set?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn ON the ignition, leaving the engine OFF.
2. Backprobe the MAF sensor signal circuit at the PCM using a digital multimeter (DMM) connected to ground.
3. Measure the voltage.

Is the voltage within the specified range?

1.0-1.6 V

Go to Step 5

Go to Step 6

5 | Important: The MAF sensor readings vary with the air temperature and the barometric pressure. The specifications indicated are at 20°C (68°F) and sea level.

1. Leave the DMM connected.
2. Start the engine.
3. Measure the voltage while briefly increasing the engine speed to approximately 4,000 RPM . Refer to the Test Description.

Does the voltage increase to approximately the specified value when the engine speed is increased?

3.0 V

Go to Step 10

Go to Step 11

6 |

1. Turn OFF the ignition.
2. Disconnect the MAF sensor electrical connector.
3. Probe the MAF sensor ground circuit using a test lamp connected to B+.

Is the test lamp illuminated?

--

Go to Step 7

Go to Step 8

7 |

1. Check for a faulty connection at the MAF sensor and at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 9

8 | Repair the open in the ground circuit to the MAF sensor. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 12 | --
9 |

1. Check for a short circuit in the MAF sensor signal circuit.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 11

10 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 12 | --
11 | Replace the MAF sensor. Refer to Mass Airflow Sensor Replacement . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on the scan tool?

--

Go to Diagnostic Trouble Code (DTC) List

System OK