Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Vacuum cut valve bypass valve harness is open or shorted - Vacuum cut valve bypass valve electrical circuit poor connection - Faulty Vacuum cut valve bypass valve

When Detected

- An improper voltage signal is sent to ECM through vacuum cut valve bypass valve.

Description

The vacuum cut valve and vacuum cut valve bypass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister. The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve bypass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve bypass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then bypassed to apply intake manifold vacuum to the fuel tank.