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.
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HOMESERVICE MANUALSCHEVROLET1997ASTRO VAN 2WD V6-4.3L VIN WREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSDESCRIPTION AND OPERATIONPRIMARY SYSTEM BASED DIAGNOSTICSEVAP PURGE SYSTEM SWITCH
1997 Chevrolet Astro Van 2WD V6-4.3L VIN W
EVAP Purge System Switch
1997 Chevrolet Astro Van 2WD V6-4.3L VIN WSECTION EVAP Purge System Switch
EVAP System:
The Evaporative Emission (EVAP) control system uses a switch located in the purge line between the canister and the purge valve to detect when purge is occurring. This switch senses the flow from the engine through the purge valve. When no purge is present, the switch is closed, applying a 12 volt signal to the control module as a NO PURGE signal. When canister purging occurs, the switch opens, interrupting off the 12 volt signal to the control module. A scan tool display will indicate that purge is occurring.
Clogging of the canister fresh air vent could allow the purge hose between the switch and canister to trap vacuum with the purge valve closed. This would result in a diagnostic indication of a purge valve stuck open or a vacuum switch failure. Similarly, leaks or blockages in the purge hoses may result in misdiagnosis of the purge valve or vacuum switch.
When servicing a purge valve diagnostic trouble code, check the canister fresh air vent, vacuum switch and the integrity of all purge hoses prior to servicing the valve.
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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.