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 MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 145 (ENGINE CONTROL SYSTEM - SYSTEM & COMPONENT TESTING)EMISSION SYSTEMS & SUBSYSTEMSEVAPORATIVE EMISSION CONTROL SYSTEM DIAGNOSISEVAP PRESSURE SWITCHING SOLENOID INSPECTION
1999 GMC Forward Control 5.7 R, Automatic
EVAP Pressure Switching Solenoid Inspection
1999 GMC Forward Control 5.7 R, AutomaticSECTION EVAP Pressure Switching Solenoid Inspection
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.
- Remove the EVAP pressure switching solenoid.
- Using DMM, measure the resistance of the EVAP pressure switching solenoid. See Fig 1 . The EVAP pressure switching solenoid resistance should be 37-44 ohms at 68°F (20°C).
- Replace the EVAP pressure switching solenoid if the resistance is not as specified. The solenoid will damage the PCM, if the resistance value is less than 27 ohms.
- Check for continuity on each terminal to the valve body. See Fig 2 .
- Replace the EVAP pressure switching solenoid if continuity is present.
- Blow air into the inboard port. The air should NOT flow through the valve and out of the outboard port.
- Apply battery voltage across the terminals of the EVAP pressure switching solenoid. See Fig 3 .
- Blow air into the inboard port and air should flow through the valve and out of the outboard port. See Fig 3 .
- Replace the EVAP pressure switching solenoid if the solenoid failed either test.
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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.