CNG

This is an Open Loop mode. When the system is activated by the ignition switch the following actions occur:
- The Powertrain Control Module (PCM) pre-positions the idle air control motor based on engine coolant temperature
- The PCM determines atmospheric air pressure from Manifold Absolute Pressure (MAP) sensor input to determine basic fuel strategy
- The PCM monitors engine coolant temperature sensor input.
- The PCM monitors CNG fuel temperature sensor input
- The PCM monitors CNG fuel low-pressure sensor input
- Intake manifold air temperature sensor input is monitored
- Throttle position sensor (TPS) is monitored
- The high-pressure fuel shut-off solenoid is energized by the powertrain control module (PCM) through the CNG high-pressure fuel shut-off solenoid relay. This solenoid will operate for approximately 2 seconds unless the engine is operating or starter motor is engaged
- The O2S sensor heater element is energized through the automatic shut-down (ASD) relay Although, O2S input is not used by the PCM to calibrate air-fuel ratio during Open Loop mode of operation