Combination Valve; Cylinder Head; Control Of Ecm - Subaru 2007 B-9 Tribeca Technicians Reference Booklet

2007 New Model Update

Combination Valve

The Combination valve is composed of a solenoid, air valve and reed valve. The solenoid operates
the air valve which allows fresh air from the secondary air pump to flow to the back side of the reed
valve. The exhaust pulses of each cylinder control the reed valve. As the exhaust stroke begins the
pressure of the exhaust closes the reed valve. As the exhaust pressure reduces, the reed valve
opens, as the fresh air pressure is now higher than the exhaust pressure. Fresh air enters the
exhaust stream and the ignition of unburned exhaust emissions begins. The reed valve will remain
open until the exhaust pressure increases.

Cylinder head

Air passages are machined inside the cylinder head as shown below. The air compressed from the
combination valve is emitted to the backside of the exhaust valve through the air passages.

Control of ECM

ECM measures engine coolant temperature, starting condition from the starter signal and other
signals, and activates air suction pump and combination valve according to the engine coolant
temperature.
The ECM will activate the combination valve relays and the pump relay when the engine coolant
temperature is below 150 degrees F (70 degrees C)
The system will operate for 90 seconds (varies according to the coolant temperature)
* Refer to STIS (Subaru Technical Infromation System)
2007 Legacy Page 68
(916)
*** New Feature
July 2006