For 1990-2009 cars

### Circuit Description

The DTC P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency diagnostic monitors the mass air flow sensor signal. The MAF sensor measures the amount of air passing through the sensor and into the intake manifold. 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 engine's fuel requirements by monitoring the current flow on the signal wire from the 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 LH 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

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

• | Condition is present for longer than 5 seconds.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will illuminate.

• | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

• | The PCM will enter the Fail-Safe Function and determine injector drive time according to TP sensor and engine speed.

• | PCM will change Idle Air Control (IAC) valve duty.

• | PCM will change fuel injectors frequency.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn off after three consecutively passing cycles without a fault present.

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

• | DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.

### Diagnostic Aids

Check for any of the following conditions:

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

• | A misrouted wiring harness-- Inspect the MAF sensor harness to ensure that it 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 connectors and wiring harnesses related to the MAF sensor. A change in the display will indicate the location of the fault.

• | Check for a restriction -- 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 1.1 to 2.9 L/sec at idle to 5 to 9 L/sec at 2,500 RPM.

If the 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 electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If you cannot duplicate the DTC P0103, 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 Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and to 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 the Freeze Frame data in order to determine when the DTC set. Always record this information.

4. Normal voltage at idle for the MAF sensor signal circuit should be 1.7 volts to 2.0 volts. This voltage reading should increase steadily to 5 volts when engine speed is increased to approximately 4000 RPM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

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

Is the MAF sensor display above the specified value?

1.1-2.9 L/sec

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 observed.

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 DMM connected to ground.
3. Measure the voltage.

Is the voltage within the specified value?

1.0-1.6 volts

Go to Step 5

Go to Step 6

5 | Important: MAF sensor readings vary with the air temperature and 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 increasing the engine speed to approximately 4000 RPM (briefly).

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

From 1.6 volts at idle up to 3.0 volts at 4000 RPM

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+.

Did the test lamp illuminate?

--

Go to Step 7

Go to Step 8

7 |

1. Check for a faulty connection at the MAF sensor and at the PCM.
2. Repair as necessary

Was a repair necessary?

--

Go to Step 12

Go to Step 9

8 | Locate and repair the open circuit 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 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement 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. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 13

Go to Step 2

13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK