BI-Fuel/Alternative Fuels

CIRCUIT DESCRIPTION
The gasoline control module (VCM/PCM or ECM) monitors the Crankshaft Position Sensor (CKP) signal in order to determine engine speed. The gasoline control module signals engine speed to the Alternative Fuels ECM by pulse-width-modulating the engine speed signal circuit.

This DTC is used to indicate no engine speed signal is being monitored by the Alternative Fuels ECM while the MAF sensor signal indicates the crankshaft is rotating.

CONDITIONS FOR RUNNING THE DTC
^ The engine is operating on alternative fuel for an initial failure. The Alternative Fuels ECM will run this DTC in gasoline mode after an initial alternative fuel mode failure.
^ No Alternative Fuels ECM MAF sensor DTCs are set this ignition cycle.
^ The MAP sensor signal indicates 105.23 kPa (31.07 in Hg) or less.
^ The mass air flow is more than 3 grams per second for 1 second continuously.

CONDITIONS FOR SETTING THE DTC
The Alternative Fuels ECM does not monitor an engine speed signal (Tach) during the 1 second that mass air flow is more than 3 grams per second.

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). Initial Inspection and Diagnostic Overview Intermittent Conditions

TEST DESCRIPTION

Steps 1-9:

Steps 10-13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if the condition affects the gasoline control module.
3. This step determines if the fault is present.