Air Switching/Relief Valve
This valve directs air injection flow to either the location near exhaust ports or to 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 a computer controlled vacuum solenoid, causes switching valve to open. This allows air pump airflow into exhaust ports.
When 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 downstream injection point.