Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1
   
   This step inspects for proper initial MIL operation.
2. 2
   
   If the scan tool fails to turn ON, check scan tool operation on a known-good vehicle. The Data Link Connector (DLC) supplies the scan tool with a power circuit (terminal No. 16) and 2 ground circuits (terminals No. 4 and 5). All 3 circuits are required for proper scan tool operation.
3. 4
   
   Both control modules simultaneously test certain DTCs regardless of the fuel system that is in operation.
4. 5
   
   Checking for a shorted MIL circuit and proper control module operation of the MIL circuit.
5. 7
   
   The Fuel Indicator Lamp (FIL) located within the fuel gauge select switch button will illuminate when the engine is operating on gasoline.

   The AFO Signal Command scan tool parameter will indicate the Alternative Fuels ECM's commanded state of the Alternative Fuel Operation circuit. The AFO Signal parameter will indicate the gasoline control modules monitored state of the Alternative Fuel Operation circuit. Regardless of the fuel system in operation these 2 data parameters will always indicate the same data unless an Alternative Fuel Operation circuit fault is present or the gasoline control module is programmed with standard gasoline software.

6. 8
   
   If actual and typical data values are different and a fault is suspected check the DTC information with a scan tool and verify that the suspected component or system DTCs have ran and passed. If they have passed use the sensor information in Description and Operation to help diagnose suspected sensor faults. If a system fault is suspected - EGR operation, EVAP operation, etc., see the DTC that applies to the system and if possible use the diagnostic test to aid in diagnosis.
7. 10
   
   DTC P1665 may set if there is an AFO Signal circuit fault or if the PCM is programmed with standard gasoline software.
8. 12
   
   Check for applicable bulletins before proceeding with DTC diagnosis.

   After determining which control module has stored DTCs, diagnose DTCs in the following order:

   • Control module memory or internal fault DTCs; PCM Memory, PCM Not Programmed, etc.
   • System and ignition voltage DTCs; System Voltage High or Low, etc.
   • Component/circuit DTCs; TP Sensor Circuit Voltage High or Low, Oxygen Sensor Circuit Insufficient Activity, etc.
   • System DTCs; MAP System Performance, TP Sensor Performance, etc.