Circuit Description

Evaporative (EVAP) emissions canister purge is controlled by a solenoid valve which allows ported vacuum to purge canister when energized (purge on) by PCM. A vacuum switch in purge line is used to detect when system is being purged. PCM supplies and reads EVAP purge vacuum switch signal. If switch is open (purge detected) when not commanded by PCM, DTC P1441 is set.

Conditions required to set DTC are:

• No ECT, IAT, MAF, MAP, or TP sensor DTCs set.
• BARO more than 85 kPa.
• ECT less than 158°F (70°C).
• Start-up IAT and ECT above 41°F (5°C).
• Difference between ECT and IAT less than 45°F (25°C).
• TP indicating a throttle position above 14 percent.
• Battery voltage is 11-16 volts.
• Engine speed above 800 RPM.
• EVAP canister purge duty cycle below 1 percent.
• EVAP canister purge vacuum switch open.
• All listed conditions present for 3 seconds.