Three-Way Solenoid Valve (TWSV)

Disconnect the hoses connecting the TWSV to the EGR valve and the EGR modulator. Connect test hoses to the TWSV. See Fig 1 . Blow into test hose No. 1, checking that air escapes from test hose No. 2.
Disconnect TWSV electrical connector and connect 12-volt battery to connector terminals. See Fig 1 . With battery connected, blow into test hose No. 1, checking that air escapes from TWSV filter and not test hose No. 2. If TWSV does not operate properly, replace with a new unit. Reconnect hoses and electrical connector.

Fig 1: Testing the Three-Way Solenoid Valve