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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD (LPG) 🢒 DTC 🢒 DTC P0103

Circuit Description

The mass air flow (MAF) sensor is an air flow meter. The MAF sensor is supplied ignition voltage and a ground. The MAF sensor heats a wire grid or a small wire within the sensor to a predetermined temperature. As inlet air flows across and cools the wire grid, the MAF sensor must increase current flow to the wire grid in order to maintain a constant wire grid temperature. The MAF sensor converts the required wire grid current flow into a frequency signal. The powertrain control module and the Alternative Fuels ECM monitor the MAF signal circuit frequency and determine the flow and mass of the air entering the engine.

The PCM and the Alternative Fuels ECM convert the MAF signal circuit frequency into a grams per second value. At idle the MAF sensor will produce a low frequency signal, around 2,000 Hz or 6 grams per second. At wide open throttle the MAF sensor will produce a high frequency signal, around 9,000 Hz or 125 grams per second).

This DTC indicates a MAF sensor frequency that is above the normal operating range of the sensor.

Conditions for Running the DTC

Power-Up Test

    • The engine is operating on alternative fuel.
    • The battery voltage is more than 10 volts.

Cranking Test

    • The engine is cranking on alternative fuel, but has not yet started.
    • The battery voltage is more than 8 volts.

Running Test

    • The engine is operating on alternative fuel.
    • The engine has been operating for more than 10 seconds.
    • The battery voltage is more than 10 volts.
    • The engine speed is more than 500 RPM.

Conditions for Setting the DTC

All Tests

The Alternative Fuels ECM monitors a MAF sensor signal of more than 10,390 Hz for at least 0.5 seconds continuously.

Action Taken When the DTC Sets

The Alternative Fuels ECM will switch-over to gasoline fuel operation. Alternative fuel operation will not be attempted until the next ignition key cycle.

    • The Alternative Fuels ECM will illuminate the MIL and store the DTC as History during 1 drive trip in which the diagnostic runs and fails.
    • The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • The Last Test Failed status will clear when the DTC runs and passes.
    • The Alternative Fuels ECM will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
    • The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared with a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • A mis-routed harness. Inspect the MAF sensor harness for routing that is too close to the following components:
       - Secondary ignition wires or coils
       - Solenoids
       - Relays
       - Motors
    • The throttle plate for sticking, or for deposits on the throttle plate, or in the throttle bore.
    • Any un-metered air that enters the engine may cause this DTC to set. Make sure that the oil dip stick is seated, and the oil fill-cap is secure.

For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

  1. This step determines if the condition is present.

    2.

  2. This step determines if the condition affects the PCM.

    3.

  3. This step determines if the MAF sensor is generating the high frequency signal.

    4.

  4. This step determines if the Alternative Fuels ECM is generating the high frequency signal.

    5.

  5. This step determines if an external source is inducing a high frequency to the MAF Signal circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

  1. Observe the Freeze Frame and/or the Failure records data for this DTC.
  2. Turn OFF the ignition for 30  seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You also may operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure Records data.
  5. Observe the Diagnostic Trouble Code (DTC) Information from the following control modules with a scan tool:
    6. • Alternative Fuels ECM
    • PCM

Does the DTC fail this ignition cycle?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Start and idle the engine.
  2. With a scan tool, establish communication with the PCM.
  3. Observe the MAF sensor data parameter.

Does the MAF sensor data parameter indicate frequency more than the specified value?

10.39 kHz

Go to Step 4

Go to Step 9

4

  1. Turn OFF the ignition.
  2. Disconnect the MAF sensor connector.
  3. Start and idle the engine.
  4. Observe the MAF sensor data parameter with the engine idling.

Does the MAF sensor data parameter indicate frequency more than the specified value?

0 Hz

Go to Step 5

Go to Step 7

5

  1. Turn OFF the ignition.
  2. Disconnect the Alternative Fuels ECM connectors. Refer to Alternative Fuels Engine Control Module Replacement .
  3. Start and idle the engine.
  4. Observe the MAF sensor data parameter with the engine idling.

Does the MAF sensor data parameter indicate frequency more than the specified value?

0 Hz

Go to Step 6

Go to Step 9

6

  1. A high frequency signal may be induced on the MAF signal circuit by sources other than the MAF sensor.
  2. Inspect the vehicle for the following conditions:
    3. • A MAF signal circuit routed near secondary ignition components
    • A MAF signal circuit routed near high current components
    • High power transceivers operating in or near the vehicle
  3. Route the wiring harness correctly or remove the source of high frequency.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

7

Replace the MAF Sensor. Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 10

--

8

Important: KL6 models require a switchover to gasoline with a scan tool in order to perform the Crankshaft Position Variation Learn Procedure.

KL8 models do not require the Crankshaft Position Variation Learn Procedure.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 10

--

10
  1. Use the scan tool in order to clear the DTCs from the following control modules:
    2. • Alternative Fuels ECM
    • PCM
  2. Turn OFF the ignition for 30 seconds.
  3. 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 11

Go to Step 2

11

With a scan tool, select Capture Info in order to observe the stored information.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK