Circuit Description

A vacuum switch in the purge line is used to detect when system is being purged. The normally closed switch will open when 5 in. H2O or greater is present in purge line. Powertrain Control Module (PCM) supplies a 5-volt reference to the switch to monitor if EVAP system is functioning properly. If switch is off (no purge detected) when PCM commands purge, DTC P0441 will set.

Conditions for setting this DTC are as follows:

• Engine speed is 550-5000 RPM.
• ECT is less than 237°F (114°C) at engine start-up.
• BARO is greater than 70 kPa.
• Canister purge duty cycle is greater than 85 percent.