BI-Fuel/Alternative Fuels

Schematic:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor is a pressure sensor. The gasoline Control Module (VCM/PCM or ECM) supplies about 5 volts on the MAP sensor reference voltage circuit. The gasoline Control Module also supplies a ground circuit to the MAP sensor. When manifold vacuum is low the MAP signal voltage rises to near 4.5 volts. As manifold vacuum increases the MAP signal voltage drops to around 1 volt. The gasoline Control Module and the AF ECU monitor the MAP signal circuit voltage and determine the vacuum within the intake manifold.

Certain vehicle models will also use the MAP sensor in order to determine the barometric pressure 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 a MAP sensor signal voltage that is above the normal operating range of the sensor.

CONDITIONS FOR RUNNING THE DTC
^ The engine is operating on alternative fuel.
^ The engine speed is greater than 500 RPM.
^ DTCs P0121, P0122, P0123 are not set.
^ The TP angle is less than 4 percent.

CONDITIONS FOR SETTING THE DTC
The AF ECU monitors a MAP sensor signal voltage of greater than 4.8 volts for at least 4 seconds continuously.

ACTION TAKEN WHEN THE DTC SETS
The AF ECU will switch-over to gasoline fuel operation.

The AF ECU will not attempt alternative fuel operation until the next key cycle.
^ A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History.
^ The AF ECU will illuminate the MIL and store the DTC as History after TWO consecutive drive trips that the diagnostic runs and fails.
^ The AF ECU 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 AF ECU 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 ECU/VCM/PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is inconsistent and should not be performed.

DIAGNOSTIC AIDS
Fault Not Present
Fault Not Present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to 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 the Diagnostic System Check - Alternative Fuels (Computers and Control Systems). Intermittent Conditions

TEST DESCRIPTION

Steps 1-10:

Steps 11-17:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the failure condition affects the gasoline control module.
3. This step determines if the failure condition is present.
5. This step determines if the MAP sensor is the shorted condition.
6. This step determines if an open sensor ground condition is present.
7. This step determines if the 5-volt reference circuit is shorted to a voltage. The maximum output that the gasoline control module should supply on the 5-volt reference circuit is 5.2 volts.