Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
Canister purge is controlled by a solenoid valve that allows ported vacuum to purge canister when energized. VCM supplies ground to energize solenoid valve which is pulse width modulated. Duty cycle is determined by closed loop feedback from HO2S. Duty cycle is calculated by VCM and output is commanded when certain conditions have been met.
A vacuum switch in purge line is used to detect when system is being purged. Normally closed switch will open when less than one in. Hg is present in purge line. VCM supplies a 12-volt reference to switch to monitor if evaporative emission control system is operating properly. DTC will set if switch is open when VCM is not commanding purge.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.