Powertrain Management (CNG)

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 toIntermittent Conditions (Symptom Related Diagnostic Procedures) .


Test Description

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the condition is present.
3. This step determines if the condition affects the PCM.
4. This step determines if the MAF sensor is generating the high frequency signal.
5. This step determines if the Alternative Fuels ECM is generating the high frequency signal.
6. This step determines if an external source is inducing a high frequency to the MAF Signal circuit.