Shut-Off Valve (Bi-Fuel)

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Fig 1: Identifying Shut-Off Valve Input And Output Signals (Bi-Fuel)

Courtesy of VOLVO CARS OF NORTH AMERICA.

The rear electronic module (REM) (4/58) controls the shut-off valves, (8/88-90) (CNG) and (8/76) (LPG), via a directly connected relay (2/140) which supplies the valves with power when they should be open.

The rear electronic module (REM) receives information via the control area network (CAN) from the engine control module (ECM) (4/46) indicating that the car should run on gas/LPG. The rear electronic module (REM) also receives information via the control area network (CAN) from the central electronic module (CEM) (4/56) indicating the position of the ignition and data about collision status. When the ignition is on and no collision has been registered, the rear electronic module (REM) activates the relay, which supplies the valves with power.

The rear electronic module (REM) deactivates the relay in the following cases:

there is a signal from the engine control module (ECM) indicating that gasoline operation has been selected
ignition off
the collision status changes
there is a fault in the communication on the controller area network (CAN).

The relay can be activated via a diagnostic command to, for example, allow the tank to be drained. Activation is carried out in appropriate diagnostics tool via the vehicle communication socket. See function group 3, Rear Electronic Module (REM).