Air Switching Valve
This valve directs air injection flow to either the location near the exhaust ports or to the downstream injection point. It also serves as a relief valve at high engine speeds.
A vacuum signal, from either a coolant control engine vacuum switch (CCEVS) or vacuum solenoid, causes the switching valve to open. This allows air pump air flow into the exhaust ports.
When the CCEVS shuts off vacuum to the switching valve, a bleed orifice in the vacuum line of the combination valve allows vacuum to go to zero. This causes the valve to switch air pump air to the downstream injection point.