Circuit Description

Multi-Ram system uses variable air induction tuning to achieve maximum performance and efficiency over entire operating range of engine. System consists of 2 main components. Intake manifold contains intake plenum switchover valve. This vacuum operated valve is essentially a moveable divider that changes airflow characteristics of intake manifold. Vacuum to valve is controlled by an ECM controlled solenoid valve.

Intake resonance switchover valve is located in air intake duct assembly in front of engine. This vacuum operated valve is also a moveable divider that changes tuning of air intake system. Vacuum to valve is controlled by ECM controlled solenoid valve. By opening and closing these valves independently in different combinations, 4 different air flow configurations can be created, each optimized to a particular set of engine operating conditions.

Both solenoid valves are supplied power via main relay (switched battery feed circuit). Both solenoid valves have a control circuit to ECM. ECM controls a valve by grounding control circuit via an internal driver. Primary function of driver is to supply ground for component being controlled. Each driver has a fault line which is monitored by ECM. When ECM is commanding a component on, control circuit voltage should be low (near zero volts). When ECM is commanding control circuit to a component off, circuit voltage should be high (near battery voltage). If fault detection circuit senses a voltage other than what is expected, this DTC will set.

ECM will monitor circuit for short to ground, short to voltage, open or an internally shorted or excessively low resistance in circuit. When ECM detects any of these malfunctions, this DTC will set and affected driver will be disabled. ECM will continue to test circuit and if fault disappears, driver will be reactivated.