DR-21A Air Switching System

Complete Driveability Test 20-Step D, before proceeding.
This test must be performed with engine at NORMAL operating temperature.
1. Disconnect upstream and downstream air hoses from air switching valve.
2. Disconnect and plug vacuum supply line to the air switching valve, then start the engine.
3. If air flows only from the downstream port, proceed to Step B.
4. If air flows only from the upstream port, replace air switching valve.
5. If no air flows from either port, repair or replace air pump as necessary.