GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) 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 MAF sensor has the following circuits:

    • An ignition 1 voltage circuit
    • A ground circuit
    • A signal circuit

The PCM 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. If the PCM detects a frequency signal that is more than the possible range of a correctly operating MAF sensor, DTC P0103 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency

Conditions for Running the DTC

    • The engine is running for more than 5 seconds.
    • The engine speed is more than 500 RPM.
    • The ignition 1 signal is more than 11 volts.
    • The above conditions are met for more than 2.5 seconds.
    • This DTC runs continuously within the enabling conditions.

Conditions for Setting the DTC

The PCM detects that the MAF sensor frequency signal is more than 11,000 Hertz for more than 3 seconds.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

    • Inspect the air induction system for any water intrusion. The water rapidly cools the hot sensing elements in the sensor causing a false indication of excessive air flow. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
    • A poor connection at the fuse for the ignition 1 voltage circuit of the MAF sensor may cause this DTC to set.
    • If the condition is intermittent, refer to Inducing Intermittent Fault Conditions and Intermittent Conditions .

Test Description

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

  1. This step tests for electromagnetic interference (EMI) on the signal circuit of the MAF sensor. A frequency reading with the MAF sensor disconnected may indicate an EMI related fault or a poor connection at the PCM. Disconnecting the MAF sensor may set additional related DTCs.

  2. This step determines if incorrect harness routing has caused this DTC to set.

  3. This step determines if water intrusion has caused this DTC to set.

  4. This step determines if high resistance at any point in the ignition 1 voltage circuit has caused this DTC to set.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 90 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Disconnect the mass air flow (MAF)/intake air temperature (IAT) sensor.
  3. Start the engine.
  4. Select the Induction Data List.
  5. Observe the MAF Sensor parameter with a scan tool.

Is the MAF Sensor parameter more than the specified value?

0 Hz

Go to Step 5

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Review the schematics for the MAF/IAT sensor.
  3. Connect a jumper wire between each of the five terminals of the MAF/IAT sensor harness connector and the corresponding five terminals of the MAF/IAT sensor. Refer to Probing Electrical Connectors and Using Fused Jumper Wires .
  4. Start the engine and allow it to reach operating temperature.
  5. Measure the frequency from the signal circuit of the MAF sensor to a good ground with a DMM. Refer to Measuring Frequency .

Does the DMM display a frequency within the specified range?

1600-2500 Hz

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition.
  2. Inspect the harness of the MAF sensor for incorrect routing that is too close to the following components:
  3. • Any aftermarket accessories--Refer to Checking Aftermarket Accessories .
    • Any solenoids
    • Any relays
    • Any motors
    • Any improperly grounded component

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Inspect the air induction system for any water intrusion.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the ignition 1 voltage circuit of the MAF sensor for the following conditions:

    • An intermittent high resistance in the circuit and the connections
    • An intermittent high resistance at the fuse in the underhood fuse block.

Refer to the following:

    •  Circuit Testing
    •  Wiring Repairs
    •  Connector Repairs

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

8

Test for an intermittent and for a poor connection at the MAF sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the MAF/IAT sensor. Refer to Mass Airflow Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

--

12

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 90 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 13

13

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK