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
The Evaporative Emission (EVAP) system is used to store fuel vapors to reduce amount of unburned fuel from escaping into atmosphere. PCM monitors the EVAP system for circuit faults in the fuel tank pressure sensor, EVAP purge solenoid and EVAP vent solenoid circuits. PCM also monitors the EVAP system for small and large leaks. During DTC diagnostic, the EVAP purge solenoid is commanded on (open) and EVAP vent solenoid is commanded on (closed) in order to build vacuum. Once vacuum is obtained, EVAP vent solenoid is commanded off and vacuum should decrease rapidly. DTC will set when vacuum decay is too slow, indicating a blocked vent system.
The following are possible conditions indicating a blocked vent system:
- EVAP purge solenoid is commanded on (open).
- EVAP vent solenoid is commanded off (open).
- Engine run time greater than 2 seconds.
- Fuel tank level between 15-85 percent full.
- BARO greater than 81 kPa.
- ECT and IAT at start-up between 41-90°F (5-32°C).
- ECT and IAT within 50°F (10°C).
- No ECT, fuel tank pressure, IAT, MAP or VSS DTCs set.
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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.
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