Theory Of Operation

WARNING: This page is about a different car, the 2013 RAM 2500 HD and 2012 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.

The CNG Shut-off Relay is used to control the power supply to both of the Fuel Tank Solenoids and the Fuel Pressure Regulator Solenoid. The CNG Shut-off Relay coil is supplied 12 volts from the ASD Relay. The Powertrain Control Module (PCM) controls the operation of the relay through a low side driver. When the PCM determines to switch the vehicle to CNG mode, it will turn on the relay, which provides 12 volts to all three solenoids. The solenoids will then open allowing CNG gas to reach the CNG Fuel Rail Assembly. The solenoids are all normally closed, blocking flow of CNG when there is no voltage supplied. When refilling the tanks, one way valves inside the Fuel Tank Solenoids will allow fuel to enter the tanks without energizing the solenoids.