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 SYSTEMSTESTING AND INSPECTIONCOMPONENT TESTS AND GENERAL DIAGNOSTICSSYSTEM DIAGNOSIS - EVAP CONTROLSYSTEM CHECK
1997 Chevrolet Astro Van 2WD V6-4.3L VIN W
System Check
1997 Chevrolet Astro Van 2WD V6-4.3L VIN WSECTION System Check
Diagnostic Chart:
Diagnostic Chart:
Circuit Description
Applying a vacuum to the EVAP system and monitoring for a vacuum decay checks the evaporative emission system. The Control Module monitors the vacuum level through the fuel tank vacuum sensor signal. At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid turn ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve turns OFF, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, when all other variables remain constant. A leak, blockage or faulty component in the system causes a DTC to set.
Diagnostic Aids
Check for the following conditions:
Poor connection at the Control Module. Inspect the harness connectors for the following conditions:
- Backed out terminals.
- Improper mating.
- Broken locks.
- Improperly formed or damaged terminals.
- Poor terminal to wire connections.
^ A damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Vacuum display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.
^ An incorrect purge or vacuum source line routing. Verify that the source vacuum and purge lines to the EVAP canister purge valve are not switched.
Refer to Carbon Particle Removal from EVAP System before starting repairs.
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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.