Test Description
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2002 Saturn SL2, 2002 Saturn SL1, 2002 Saturn SL, 2002 Saturn SC2, and 2002 Saturn SC1. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedures.
- 1
The System Check must be performed before proceeding with this diagnostic test. Failure to perform the System Check will result in misdiagnosis. - 2
This step checks the battery voltage supply from the lock-off relay to the LPL. The lock-off relay is energized regardless of which fuel system is operating the vehicle. - 3
This step checks the AF ECM and the Low Pressure Lock-Off Solenoid Control circuit for proper operation. The test lamp should illuminate for a few seconds then turn OFF as the engine cannot start on CNG with the LPL disconnected. - 4
This step checks the battery voltage supply from the lock-off relay to the HPL. The lock-off relay is energized regardless of which fuel system is operating the vehicle. - 5
This step check the AF ECM and the High Pressure Lock-Off Solenoid Control circuit for proper operation. The test lamp should illuminate for a few seconds then turn OFF as the AF ECM opens the HPL for system priming prior to cranking the engine. - 6
This step checks for proper battery voltage output from the lock-off relay. - 7
This step checks for proper relay coil positive voltage and ground supply. - 8
This step checks for proper battery voltage supply from the CNG fuse (20-amp) circuit to the lock-off relay. If the test lamp fails to illuminate the failure can only exist between the relay and the circuit splice. For example: a blown fuse would cause a lack of power to the AF ECM causing no scan tool communication in which the OBD System Check would have directed you to a different diagnostic procedure. - 9
This step checks for proper positive voltage supply from the gasoline fuel pump circuit to the lock-off relay.