BI-Fuel/Alternative Fuels

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 gasoline Control Module (VCM/PCM or ECM) and the Alternative Fuels ECM monitor the MAF signal circuit frequency and determine the flow and mass of the air entering the engine.

The gasoline Control Module (VCM/PCM or ECM) and the Alternative Fuels ECM convert the MAF signal circuit frequency into a grams per second value. During low air flow rates (such as at engine idle), the MAF sensor will produce a low frequency signal (around 2,000 Hz or 6 grams per second). During high air flow rates, such as at wide open throttle-road load, the MAF sensor will produce a high frequency signal (around 9,000 Hz or 125 grams per second).

The gasoline Control Module (VCM/PCM or ECM) and the Alternative Fuels ECM monitor the actual MAF sensor air flow rate and compare the actual air flow rate to a calculated air flow rate. The calculated air flow rate is based upon engine speed and Barometric Pressure (BARO). The gasoline Control Module and the Alternative Fuels ECM use the MAP sensor in order to determine the BARO when the ignition switch is turned ON and the engine is NOT cranked. This BARO reading may also be updated whenever the engine is operated at wide open throttle.

This DTC is used to indicate that the actual MAF sensor air flow rate does not match a calculated air flow rate.

CONDITIONS FOR RUNNING THE DTC
^ The engine is operating on alternative fuel.
^ No Alternative Fuels ECM, ECT, TP, IAT, MAP, or MAF sensor DTCs are set.
^ The engine has been operating for more than 10 seconds.
^ The engine speed is more than 500 RPM.
^ The battery voltage is more than 10 volts.
^ The MAP sensor performance DTC P0106 has run at least once this ignition cycle.

CONDITIONS FOR SETTING THE DTC
The Alternative Fuels ECM monitors an actual MAF sensor air flow rate that does not match a calculated air flow rate for at least 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 using a scan tool.
^ Interruption of Control Module (AF ECM/VCM/PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is in-consistent and should not be performed.

DIAGNOSTIC AIDS

Intermittent Condition
A fault not present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to the Intermittent Conditions diagnostic information located in symptoms - Computers and Control Systems. If any additional DTCs were stored proceed to the applicable DTC table in the order stated in Diagnostic System Check - Alternative Fuels (Computers and Control Systems). Intermittent Conditions Initial Inspection and Diagnostic Overview

TEST DESCRIPTION

Steps 1-6:

Steps 7-10:

The numbers below refer to the step numbers on the diagnostic table.
2. When a DTC fails, some data parameters are recorded and stored for possible diagnostic aid. This stored data (Freeze Frame/Failure Records) can be saved into a scan tool and be reviewed later if necessary in order to help diagnose an intermittent or difficult to reproduce condition.
3. Any stored sensor/circuit DTCs should be diagnosed prior to diagnosing this (system type) DTC.
5. This DTC determines the calculated air flow based upon the MAP sensor values. The MAP sensor must accurately display manifold pressure in order for this DTC to compare the MAF sensor airflow to the calculated air flow correctly.
A fault not present will be indicated by the MAP Sensor Performance DTC if the MAP sensor is functioning correctly.
6. This DTC determines the calculated air flow based upon the TP sensor values. The TP sensor must accurately display throttle angle in order for this DTC to compare the MAF sensor airflow to the calculated air flow correctly.
A fault not present will be indicated by the TP Sensor Performance DTC if the TP sensor is functioning correctly.